Late transition metal organometallic chemistry. rhodium, iridium and gold complexes with sigma and pi hydrocarbon-based ligands.

UNIVERSIDAD DE SEVILLA CONSEJO SUPERIOR DE INVESTIGACIONES CIENTÍFICAS Departamento de Química Inorgánica Instituto de Investigaciones Químicas Late Transition Metal Organometallic Chemistry. Rhodium, Iridium and Gold Complexes with σ and π Hydrocarbon-Based Ligands. María Fernández-Espada Pastor Tesis Doctoral Sevilla, 2015 Late Transition Metal Organometallic Chemistry. Rhodium, Iridium and Gold Complexes with σ and π Hydrocarbon-Based Ligands. por María Fernández-Espada Pastor Trabajo presentado para aspirar al Título de Doctora en Química Sevilla, 2015 María Fernández-Espada Pastor Directores de Tesis: Manuel López Poveda Ernesto Carmona Guzmán Profesor de Investigación Catedrático de Química Inorgánica (CSIC) (Universidad de Sevilla) TABLE OF CONTENTS Abbreviations 1 Consideraciones Generales 5 General Considerations 10 Chapter I. Organometallic Compounds of Gold(I) Stabilized by Coordination to a Terphenylphosphine Ligand. I.1. Prologue 24 I.2. Introduction 25 I.3. Results and Discussion 37 I.3.1. Mononuclear Au(I) Derivatives Containing the Phosphine PMe2ArDipp2 (ArDipp2 = C6H3-2,6-(C6H3-2,6-iPr2)2; Dipp = 2,6- iPr2C6H3) 37 I.3.1.1. Synthesis and Characterization of the Au(I) Chloride Complex [AuCl(PMe2ArDipp2)] (1) 37 I.3.1.2. Synthesis and Characterization of the Triflimide (NTf2; Tf = SO2CF3, 2) and Mesylate (Ms; Ms = SO3Me, 3) Analogues of Complex 1 39 I.3.1.3. Cationic Adducts of Formula [Au(PMe2ArDipp2)L][NTf2] (L = NCMe, 4; THT, 5) 42 I.3.1.4. Synthesis and Characterization the of Au(I) Hydrocarbyl Complexes [AuR(PMe2ArDipp2)], R = Me, 6a; Et, 6b; CH2CMe2Ph, 6c; Ph, 6d; CH=CH2, 6e; C≡CH, 6f) 44 I.3.1.4.1. Nuclear Magnetic Resonance Spectra of Complexes 6a-6f 46 I.3.1.4.2. X-ray Molecular Structures of Complexes 6b, 6e and 6f 52 I.3.2. Cationic Hydrocarbyl-Bridged Digold(I) Complexes of Formula [Au2( µ 2-R)(PMe2ArDipp2)2][NTf2] (R = Me, 7a; Et, 7b; CH2CMe2Ph, 7c; Ph, 9; CH=CH2, 10; C≡CH, 11) 58 I.3.2.1. Synthesis and Characterization of the Cationic gem-σ,σ- Diaurated Alkyl Complexes [Au2(µ2-R)(PMe2ArDipp2)2][NTf2] (R = Me, 7a; Et, 7b; C2H2CMe2Ph, 7c) 59 I.3.2.2. Synthesis and Characterization of the Cationic gem-σ,σ- Diaurated Phenyl Complex [Au2(µ2- Ph)(PMe2ArDipp2)2][NTf2] (9) 67 I.3.2.3. Synthesis and Characterization of the Cationic gem-σ,π- Diaurated Vinyl Complex [Au2(µ2- CH=CH2)(PMe2ArDipp2)2][NTf2] (10) 69 I.3.2.4. Synthesis and Characterization of the Cationic gem-σ,π- Diaurated Dinuclear Acetylide Complex [Au2(µ2- C≡CH)(PMe2ArDipp2)2][NTf2] (11) 78 I.4. Experimental Section 89 I.4.1. General Considerations 89 I.4.2. Synthesis and Characterization of the New Complexes Obtained 91 I.5. Bibliography 120 Chapter II. Organometallic Complexes of Iridium(III) with Ancillary Pentamethylcyclopentadienyl and Hydrotris(pyrazolyl)borate Ligands. II.1. Prologue 128 II.2. Introduction 129 II.2.1. C—H Activation and Cyclometallated Ligands 129 II.2.2. Cationic Ir(III) Alkylidenes 138 II.3. Results and Discussion 142 II.3.1. Reactivity of Complex 1 with Alkynes 142 II.3.1.1. Reaction of Complex 1 with NaBArF in the Presence of Acetylene 142 II.3.1.2. Reaction of Complex 1 with NaBArF in the Presence of Phenylacetylene 148 II.3.1.3. Reaction of Complex 1 with NaBArF in the Presence of Phenyl-Methyl Acetylene 159 II.3.1.4. Mechanistic and Thermodynamic Considerations 164 II.3.2. Synthesis, Characterization and Reactivity of Ir(III) Complexes Containing the Tp* Ligand 174 II.3.2.1. Synthesis of Alkylidene Complexes by Reaction with Trityl Cation (Ph3C+) 174 II.3.2.2. Deuteration of Complex 11 179 II.3.2.3. Reaction of Complex 11 with NaOH 183 II.3.2.4. Reactions of Complex 11 with Neat Acetonitrile in the Presence and Absence of Added Water 185 II.4. Experimental Section 194 II.4.1. General Considerations 194 II.4.2. Synthesis and Characterization of the New Complexes Obtained 196 II.4.3. Reaction of Complexes 11 and 14 with NaBH4 218 II.4.4. Reaction of Complex 15 with HPF6 218 II.5. Bibliography 219 Chapter III. Organometallic Rhodium Complexes with Bulky Phosphine Ligands. III.1. Prologue 227 III.2. Introduction 228 III.2.1. Organometallic Rhodium Chemistry: a Brief Overview 228 III.2.2. The Use of Bulky Phosphine Ligands in Rhodium Chemistry 233 III.3. Results and Discussion 241 III.3.1. Rhodium(I) Complexes of the Terphenyl Phosphines PMe2ArXyl2 and PMe2ArDipp2 241 III.3.1.1. Synthesis and characterization of Rh(I) Complexes of composition [RhCl(COD)(PMe2Ar’)] (2a, 2b) 242 III.3.1.2 Reaction of Complex [RhCl(COD)(PMe2ArXyl2)] (2a), with NaBArF 244 III.3.1.3. Reaction of Complexes [RhCl(COD)(PMe2Ar’)] (2a and 2b), with carbon monoxide 249 III.3.1.4. Generation of Cationic Carbonyls Derived from Complexes 5a and 5b 251 III.3.2. Synthesis, Characterization and Reactivity of (C5Me5)Rh(III) metallacycles Derived from Phosphines PR(Xyl’)2 (R = Me, Xyl’ = 2,6-Me2C6H2-4-R’ where R’ = Me, OMe, F; R = Et, Xyl’ = Xyl = 2,6-Me2C6H3) 258 III.3.2.1 Cyclometalated Rh(III) Compounds Derived from PRAr2 (R = Me, Et, Ar = p-substituted xylyl) 260 III.3.2.2. Reaction of Complexes 9b-9e with NaBArF in the Presence and in the Absence of Lewis Bases 262 III.3.2.3. Reaction of Complexes 12b-12e with Hydrogen 267 III.3.2.4. Deuteration of Hydrosilanes and Hydrosilylation of Aromatic Ketones Catalyzed by Complexes 12b-12e 272 III.4. Experimental Section 276 III.4.1. General Considerations 276 III.4.2. Synthesis and Characterization of the New Complexes Obtained 278 III.5. Bibliography 308 Conclusiones 312 7 Introducción, Resultados y Discusión, y Parte Experimental, para cada uno de los capítulos que la componen. Para facilitar su lectura, la bibliografía aparece tanto a pie de página como al final de cada capítulo, y de forma independiente en cada uno de ellos. Esta distribución hace que algunas referencias puedan aparecer en distintos capítulos. La numeración de los esquemas, figuras y compuestos es independiente en cada uno de ellos. Como parte del programa de Formación de Profesorado Universitario del Plan Propio de la Universidad de Sevilla se ha realizado una estancia breve de cuatro meses en Monash University, en Melbourne (Australia), bajo la supervisión del Prof. Cameron Jones. Por motivos de espacio, los resultados experimentales obtenidos durante dicha estancia no se han incluido en el manuscrito. Estos resultados incluyen la síntesis y reactividad de complejos de molibdeno en bajos estados de oxidación y bajo número de coordinación con ligandos amido, de tipo Ar*N(K)SiR3 y Ar*N(K)Mes (Ar* = C6H2{C(H)Ph2}2Me-2,6,4; R3 = Me3, iPr3 ó Ph3; Mes = 1,3,5-trimetilbenceno). Con el objeto de obtener la mención de Doctor Internacional (RD 99/2011; BOE 10-02-2011, Art. 15), la mayor parte de la Tesis se ha redactado en inglés, exceptuando las Consideraciones Generales del inicio y las Conclusiones finales. El primer capítulo de la presente Tesis Doctoral se ocupa del estudio de complejos y compuestos organometálicos de Au(I) con las fosfinas anteriormente comentadas del tipo PMe2Ar’, donde Ar’ = ArDipp2 = C6H3- 2,6-(2,6-iPr2C6H3)2. Los resultados más importantes incluyen la síntesis y caracterización de diversos compuestos dinucleares de oro(I) que contienen la unidad estructural [Au2(µ-R)]+, donde R = Me, Et, C6H5, CH=CH2 y C≡CH, que se estabiliza por la coordinación a los átomos de 8 oro de sendos ligandos fosfina. Este tipo de complejos dinucleares de oro tienen un gran interés en la actualidad, pues en la bibliografía reciente se han propuesto compuestos análogos como especies fundamentales en procesos orgánicos catalizados por complejos de oro, siendo los aquí descritos los ejemplos que contienen como grupos puentes los radicales hidrocarbonados más simples. El segundo capítulo se centra en la química organometálica del iridio en su estado de oxidación +3, y está subdividido en dos apartados. En el primero de ellos se describe la reactividad frente a diversos alquinos de complejos catiónicos de Ir(III) conteniendo el ligando C5Me5 estabilizados con la fosfina voluminosa ciclometalada PMeXyl2 (Xyl = C6H3-2,6-Me2). Las reacciones desarrolladas han dado lugar a diversos procesos de activación C—H y acoplamientos C—C. En la segunda parte, el ligando aniónico hidrotris(3,5-dimetilpirazolil)borato, TpMe2, que en algunos aspectos de su coordinación se asemeja al grupo C5Me5, está presente en la esfera de coordinación del iridio. Como resultados más interesantes hay que destacar la síntesis de un alquilideno catiónico ciclometalado que, en comparación con otras especies de este tipo, es muy estable térmicamente. La reacción de esta especie con acetonitrilo en presencia de agua genera un compuesto metalabicíclico con estructura semejante a la del barreleno. Finalmente el tercer capítulo versa sobre la química organometálica del rodio, y contiene dos partes bien diferenciadas. En la primera se discuten especies de Rh(I) con PMe2Ar’, aunque en este caso se estudian los ligandos en los que Ar’ = ArMes2 y ArDipp2. El trabajo ha resultado en la obtención de varios complejos de interés desde el punto de vista estructural. La segunda parte concierne al estudio de especies catiónicas de Rh(III) con el ligando pentametilciclopentadienilo, C5Me5, y una fosfina ciclometalada 9 de una familia de fosfinas menos voluminosas de composición PR(Xyl’)2 (R = Me, Xyl’ = C6H2-2,6-Me2-4-R’, donde R’ = Me, OMe, F; R = Et, Xyl’ = Xyl = C6H3-2,6-Me2). Este trabajo surge como continuación de la Tesis del Dr. Jesús Campos, en la que se estudiaron diversos procesos catalíticos, entre ellos la deuteración/tritiación de hidrosilanos y la hidrosililación de dobles enlaces C=X (C = O, N) utilizando el compuesto ciclometalado derivado de la fosfina PMeXyl2. Nuestro trabajo tiene como objetivo establecer el efecto de los sustituyentes R y R’ en las propiedades donadoras de las fosfinas, y analizar cómo estas variaciones afectan a la eficiencia catalítica del centro metálico. Una parte de los resultados obtenidos se ha publicado en forma preliminar o como trabajo completo, mientras que otras secciones son todavía inéditas. A continuación se relacionan los artículos derivados de esta Tesis que están ya publicados y se detallan, asimismo, aquéllos cuyos manuscritos están actualmente en fase de preparación. A esta relación le sigue la de los nuevos compuestos que se han obtenido y caracterizado. 10 GENERAL CONSIDERATIONS In 1952, the research groups of Wilkinson and Fischer independently proposed the sandwich structure of well-known ferrocene, thereby marking the beginning of a revival in Organometallic Chemistry, revealed by the dramatic increase in the number of new compounds, of very diverse nature, synthesized to date. As it is well known, this discipline is dedicated to the study of compounds that contain one or more metal-carbon bonds, a circumstance that has brought to light important modifications in the reactivity of the organic fragments bonded to the metal. This fact has permitted transformations impossible to achieve using classic methods and has opened a new horizon of possibilities. Thus, organometallic compounds have carved an important niche for themselves in our society and are now essential in numerous industrial processes that include, among others, the obtainment of simple organic products (e.g. acetic acid, α-olefins, diverse aldehydes, etc.), commonly used polymers and useful new materials for the electrical industry, as well as the development of new materials and of alternative energy sources. The results presented in this Thesis lie within one of the lines of investigation carried out by the group of Organometallic Chemistry and Homogenous Catalysis of the Instituto de Investigaciones Químicas (Centro Mixto Universidad de Sevilla−CSIC), that has, as an objective, the study of reactions that imply breaking and formation of C—H, C—O, C— C, and other similar bonds, selectively induced for complexes of metals from group 9 (Rh and Ir) and, for the first time in this Doctoral Thesis, group 11 (Au). It is also pertinent to note that this Doctoral Thesis is based 11 in a recently undertaken project in which the organometallic complexes of these metals contain very bulky phosphine ligands. The experiments described in this Doctoral Thesis include, among others, the synthesis of organometallic compounds of the elements Rh, Ir and Au that can contain stabilizing anionic ligands, formally tridentate, of the type pentamethylcyclopentadienyl, C5Me5, or hydrotris(3,5- dimethylpyrazolyl)borate, TpMe2, and/or bulky phosphines. The latter pertain specifically to two distinct types: first are those with composition PMe2Ar’, where Ar’ is a substituent of type terphenyl; and second, those of composition PMeAr2, with Ar being the xylyl radical or some of its simple derivatives, capable of undergoing a cyclometallation process due to the presence of methyl groups in the ortho positions of the ring. Appropriate reactivity studies are further discussed and, in cases of interest, completed with the corresponding mechanistic studies. The new synthesized compounds have been also completely characterized by NMR spectroscopy and X-ray single crystal diffraction. All the X-ray diffraction studies are the work of the author of this Thesis. In most cases, the composition of the new compounds has been deduced by elemental analysis or high-resolution mass spectrometry. For considerations of space, detailed structural data derived from X-ray studies have been incorporated in an Annex in the electronic version of this Thesis. This Thesis has a classic structure with each of the chapters containing: Prologue, Introduction, Results and Discussion, and Experimental Section. For ease of reading, the bibliography appears in both the footnotes and at the end of each chapter. This distribution may result in some of the references appearing in more than one chapter. The numbering of the Schemes, Figures and compounds is also independent by 12 chapter. As part of the programme Formación de Profesorado Unvesitario from the Plan Propio of Universidad de Sevilla I made a four-month stay in Monash University, in Melbourne (Australia), where I worked under the supervision of Prof. Cameron Jones. For reasons of space, the experimental results obtained during that stay have not been included in this Thesis. These results involved the synthesis and reactivity of molybdenum complexes, with low oxidation state and low coordination number, with different bulky amido ligands, of the type Ar*N(K)SiR3 and Ar*N(K)Mes (Ar* = C6H2{C(H)Ph2}2Me-2,6,4; R3 = Me3, iPr3 or Ph3; Mes = 1,3,5- trimethylbenzene). In order to obtain the endorsement of International Doctor (RD 99/201; BOE 10-02-2011, Art 15), most of the Thesis is written in English, with the exception of the General Considerations, which is written in Spanish and English, and the Conclusions, written only in Spanish. The first chapter of this Doctoral Thesis deals with the study of diverse complexes of Au(I) with the previously mentioned phosphines of the type PMe2Ar’, where Ar’ = ArDipp2 = C6H3-2,6-(2,6-iPr2C6H3)2. The most important results include the synthesis and characterization of a variety of dinuclear Au(I) compounds that contain the core [Au2(µ-R)]+, where R = Me, Et, C6H5, CH=CH2 y C≡CH, which are stabilized by the coordination of both phosphine ligands to the two gold centres. These types of dinuclear gold complexes are currently of great interest. Analogous compounds have been proposed in recent literature to be fundamental key species in organic processes catalyzed by gold, containing the examples described herein the simplest hydrocarbon radicals as bridging ligands. 13 The second chapter focuses on the organometallic chemistry of iridium in the oxidation state +3, and is divided into two sections. The first part describes the reactivity against various alkynes of cationic Ir(III) complexes containing the C5Me5 ligand stabilized with the cyclometallated bulky phosphine PMeXyl2 (Xyl = C6H3-2,6-Me2). The reactions developed have led to several C—H activation and C—C coupling processes. In the second part, the anionic hydrotris(3,5-dimethylpyrazolyl)borate ligand, TpMe2, which in some aspects resembles the group C5Me5, is present in the coordination sphere of the iridium centre. Some of the most interesting results are the synthesis of a cationic cyclometallated alkylidene which, compared to other species of this kind, presents a very high thermal stability. The reaction of this species with acetonitrile in the presence of water generated a metallabicyclic compound with a structure that resembles the hydrocarbon barrelene. Finally, the third chapter deals with the organometallic chemistry of rhodium and also contains two distinct parts. In the first part, the chemistry of Rh(I) with PMe2Ar’ is described, although in this case the ligands studied are those in which Ar’ = ArMes2 y ArDipp2. This work resulted in the isolation of several structurally interesting complexes. The second part concerns the study of cationic species of Rh(III) with the pentamethylcyclopentadienyl ligand, C5Me5, and a cyclometallated family of less bulky phosphines of composition PR(Xyl’)2 (R = Me, Xyl’ = C6H2- 2,6-Me2-4-R’, where R’ = Me, OMe, F; R = Et, Xyl’ = Xyl = C6H3-2,6- Me2). This work continues the Thesis of Dr. Jesús Campos, where several catalytic processes were studied, including the deuteration/tritiation of hydrosilanes and the hydrosililation of C=X (C = O, N) double bonds using the ciclometallated complex derived from the phosphine PMeXyl2. The goal of our work has been to establish the effect of the substituents R 14 and R’ in the donating properties of the phosphines, and analyse their effect in the catalytic efficiency of the metallic centre. Parts of the results were published in preliminary form or as a complete work, while other sections are awaiting publication. Below, the papers derived from the work of this Thesis are listed, as well as those manuscripts that are currently under preparation. Next are presented the new compounds that have been obtained and characterized in this work. 15 PUBLICATIONS Cyclometalated iridium complexes of bis(aryl) phosphine ligands: catalytic C—H/C—D exchanges and C—C coupling reactions. Campos, J.; Espada, M. F.; López-Serrano, J.; Carmona, E. Inorg. Chem. 2013, 52, 6694-6704. Reactivity of a Cationic (C5Me5)IrIII-Cyclometalated Phosphine Complex with Alkynes. Espada, M. F.; Poveda, M. L.; Carmona, E. Organometallics 2014, 33, 7164-7175. Water-Promoted Generation of a Diazairida Homobarrelene by C—C Coupling Between an Iridacyclic Alkylidene and Acetonitrile. Espada, M. F.; López-Serrano, J.; Poveda, M. L.; Carmona, E. Angew. Chem. Int. Ed. DOI: 10.1002/ange.201503149. 16 New Complexes Prepared in Chapter I† Tf = SO2CF3 and Ms = SO3Me † Three-center two-electron interactions (3c-2e) like those existing in complexes 7 and 9 are depicted in this Thesis using the structure-bonding representations that employ the socalled “half-arrow” notation (see J. C. Green, M. L. Green, G. Parkin, Chem. Comm. 2012, 48, 11481-11503). Chapter I. Organometallic Compounds of Gold(I) Stabilized by Coordination to a Terphenylphosphine Ligand 24 I.1. PROLOGUE The synthesis and structural characterization of a series of cationic dinuclear gol(I) complexes that contain a [Au2(µ-R)]+ core, where R stands for a simple hydrocarbyl e.g. Me, Et, Ph, CH=CH2, C≡CH and others are described in the first Chapter of this Thesis. Some species of this kind have been postulated as intermediates in catalytic transformations of unsaturated organic substrates mediated by Au(I) complexes, a very active area of research nowadays. Chapter I. Organometallic Compounds of Gold(I) Stabilized by Coordination to a Terphenylphosphine Ligand 25 I.2. INTRODUCTION This is the first PhD Thesis within our research group in which organometallic compounds of gold are studied. Hence, a brief revision of the main aspects of this area seems appropriate. The organometallic chemistry of gold is clearly dominated by compounds having the d10 metal configuration, i.e. in the +1 oxidation state, and even if important breakthroughs have been made in Au(III) catalysis, only Au(I) complexes will be considered here. The coordination number of most Au(I) complexes is two, with the corresponding ligands arranged in a linear fashion.1 The organometallic chemistry of gold is somewhat underdeveloped in comparison with other platinum-group metals. This is due not only to its prize, but also to the low coordination numbers of the Au(I) species and 1 a) C. Elschenbroich, Organometallics, 3rd Edition, WILEY -VCH Verlag GmbH & Co. KGaA, Weinheim, Germany, 2006; b) M. Bochmann, Organometallics and Catalysis. An Introduction., Oxford University Press, Oxford, UK, 2014; c) J. F. Hartwig, Organotransition Metal Chemistry: From Bonding to Catalysis, University Science Books, Sausalito, 2009; d) R. H. Crabtree, The Organometallic Chemistry of the Transition Metals, Wiley, Hoboken, NJ, 2009. Chapter I. Organometallic Compounds of Gold(I) Stabilized by Coordination to a Terphenylphosphine Ligand 26 mainly to the lack, until recently, of catalytic applications in important organic processes, such as those involving C—C and C—X (X = heteroatom) bond formation of unsaturated substrates.2 The latter area of research is now a very important one, and its development has allowed for collateral but fundamental studies that have resulted, among other accomplishments, in the recent synthesis of the first vinylidene species without stabilizing heteroatom substituents, 3 a the characterization of allenyl Au(I) and Au(III) complexes, the latter being axially chiral,3b advances in the chemistry of gold alkylidenes,3c-3d etc. The simplest Au(I) hydrocarbyls, i.e. complexes of the type L-Au- Me and [Me-Au-Me]- are quite old species,4a as it is the parent mono- 2 For reviews on this topic, see: a) T. Lauterbach, A. M. Asiri, A. S. K. Hashmi, Adv. Organomet. Chem. 2014, 62, 261-297; b) C. Obradors, A. M. Echavarren, Chem. Commun. 2014, 50, 16-28; c) C. M. Friend, A. S. K. Hashmi, Acc. Chem. Res. 2014, 47, 729–730; d) I. Braun, A. M. Asiri, A. S. K. Hashmi, ACS Catal. 2013, 3, 1902-1907; e) M. Rudolph, A. S. Hashmi, Chem. Soc. Rev. 2012, 41, 2448-2462; f) N. Krause, C. Winter, Chem. Rev. 2011, 111, 1994-2009; g) A. Corma, A. Leyva-Pérez, M. J. Sabater, Chem. Rev. 2011, 111, 1657-1712; h) A. S. K. Hashmi, Angew. Chem. Int. Ed. 2010, 49, 5232- 5241; i) H. Schmidbaur, A. Schier, Organometallics 2010, 29, 2-23; j) A. Furstner, Chem. Soc. Rev. 2009, 38, 3208-3221; k) A. S. Hashmi, M. Rudolph, Chem. Soc. Rev. 2008, 37, 1766-1775; l) E. Jiménez-Nuñez, A. M. Echavarren, Chem. Commun. 2007, 333-346. 3 a) R. J. Harris, R. A. Widenhoefer, Angew. Chem. Int. Ed. 2015, 54, 6867-6869; b) A. Johnson, A. Laguna, M. C. Gimeno, J. Am. Chem. Soc. 2014, 136, 12812-12815; c) M. Joost, L. Estevez, S. Mallet-Ladeira, K. Miqueu, A. Amgoune, D. Bourissou, Angew. Chem. Int. Ed. 2014, 53, 14512-14516; d) R. J. Harris, R. A. Widenhoefer, Angew. Chem. Int. Ed. 2014, 53, 9369-9371; e) M. W. Hussong, F. Rominger, P. Kramer, B. F. Straub, Angew. Chem. Int. Ed. 2014, 53, 9372-9375. 4 a) W. Manchot, H. Gall, Chem. Ber. 1925, 58, 2175–2178; b) A. Tamaki, J. K. Kochi, J. Chem. Soc., Dalton Trans. 1973, 2620-2626 ; c) H. Willner, J. Schaebs, G. Hwang, F. Mistry, R. Jones, J. Trotter, F. Aubke, J. Am. Chem. Soc. 1992, 114, 8972–8980; d) S. Martinez-Salvador, J. Fornies, A. Martin, B. Menjon, Angew. Chem. Int. Ed. 2011, 50, 6571-6574; e) H. V. Rasika Dias, C. Dash, M. Yousufuddin, M. Ali Celik, G. Frenking, Inorg. Chem. 2011, 50, 4253-4255. Chapter I. Organometallic Compounds of Gold(I) Stabilized by Coordination to a Terphenylphosphine Ligand 27 carbonyl AuCl(CO).4b The more interesting cationic dicarbonyl [OC-Au- CO]+ has been synthesized much more recently4c (Figure 1) and there is growing interest in other neutral and cationic gold carbonyls.3c,4d,4e Chapter I. Organometallic Compounds of Gold(I) Stabilized by Coordination to a Terphenylphosphine Ligand 28 Figure 1. Some polynuclear Au(I) organometallic species. On the other hand, while neutral monomeric [AuAr] (Ar = aryl) complexes, void of other donor ligands are very unstable species, the Et3P Au Me [Me Au Me]- OC Au Cl [OC Au CO]+ (Kochi, 1973) (Kochi, 1973) Au Au Au Au Au Au Au Au Au Au Ag + (Manchot, 1925) (Aubke, 1992) (Floriani, 1983) (Laguna, 2000) Au Au Au L LL + NN Dipp Dipp L = (Grey, Sadighi, 2012) Chapter I. Organometallic Compounds of Gold(I) Stabilized by Coordination to a Terphenylphosphine Ligand 29 related oligomeric materials [AuAr]n are well known cyclic compounds in which the aryl ligands symmetrically bridge two gold atoms. This is the structure ascertained for [AuMes]5 (Mes = mesityl = 2,4,6-C6H2Me3)5a also shown in Figure 1. In this and related structures, the distance found between the bridged Au atoms (ca. 2.70 Å) seems to indicate that they are engaged in d10–d10 bonding interactions, allowing for the introduction of the term aurophylicity, which has been explained on account of relativistic effects due to the very large nuclear charge, Z, of the gold nucleus.6 Gold(I) centres have this tendency to interact attractively among themselves and also with other d10 centers including Ag(I), as can be deduced, among others examples, from the formation of the hexametallic monocation shown in Figure 1 upon reaction of [AuMes]5, containing a five-membered gold ring, with silver triflate.7 The trinuclear complex [Au3(IDipp)3]+ that contains (Figure 1) a Dipp-substituted NHC ligand5b reported by Grey and Sadighi, features Au···Au contacts of ca. 2.65 Å and can be considered as an isolobal analogue of [H3]+, the simplest molecule with a 3c-2e bond. 5 a) S. Gambarotta, C. Floriani, A. Chiesi-Villa, C. Guastini, J. Chem. Soc., Chem. Commun. 1983, 1304-1306; b) T. J. Robilotto, J. Bacsa, T. G. Gray, J. P. Sadighi, Angew. Chem. Int. Ed. 2012, 51, 12077-12080. 6 a) H. Schmidbaur, A. Schier, Chem. Soc. Rev. 2012, 41, 370-412; b) P. Pyykkö, Angew. Chem. Int. Ed. 2004, 43, 4412-4456. 7 E. Cerrada, M. Contel, A. D. Valencia, M. Laguna, T. Gelbrich, M. B. Hursthouse, Angew. Chem. Int. Ed. 2000, 39, 2353–2356. Chapter I. Organometallic Compounds of Gold(I) Stabilized by Coordination to a Terphenylphosphine Ligand 30 Another consequence of this Au···Au bonding interaction is the stabilization of the very interesting “carbide” [(LAu)5C]+ (L = Ph3P)8,9 shown in Figure 2. As the fragment [Au(PPh3)]+ is isolobal with H+, this complex serves as a model for the CH5+ cation, a species invoked to explain certain experimental findings observed when CH4 is dissolved in superacids. 10 This isolobal relationship will resurface later, when considering the structures of some of the new Au(I) organometallic complexes described in this Chapter. Accordingly, we believe that some brief historical comments are appropriate. Figure 2. A carbon-centred pentanuclear gold-cluster. 8 F. Scherbaum, A. Grohmann, G. Müller, H. Schmidbaur, Angew. Chem. Int. Ed. 1989, 28, 463–465. 9 For some related derivatives see: a) J. Vicente, M. T. Chicote, R. Guerrero, P. G. Jones, J. Am. Chem. Soc. 1996, 118, 699–700; b) H. Schmidbaur, F. Gabbaie, A. Schier, J. Riede, Organometallics 1995, 14, 4969–4971. 10 a) G. A. Olah, G. Klopman, R. H. Schlosberg, J. Am. Chem. Soc. 1969, 91, 3261–3268; b) G. A. Olah, R. H. Schlosberg, J. Am. Chem. Soc. 1968, 90, 2726-2727. C AuL LAu AuL Au Au + L = PPh3 (Schmidbaur, 1989) L L Chapter I. Organometallic Compounds of Gold(I) Stabilized by Coordination to a Terphenylphosphine Ligand 31 The concept of isolobality was introduced by Nobel Laureate (1981) Roald Hoffmann and presented prominently with the title Building Bridges Between Inorganic and Organic Chemistry in his 1982 Nobel Lecture.11 Shortly afterwards, Stone demonstrated the value of the isolobal connection in organometallic synthesis12 and included Cu, Ag and Au fragments, MLn, among the structural units with isolobal relations with simple units like H+, CH3 and other common organic and inorganic entities. A third contribution that following Stone’s insightful views integrated metal clusters into the isolobal world was provided by Mingos,13 who also noted for gold the importance of taking into account the secondary contribution made by the 6px and 6py orbitals of gold in Au(PR3) fragments in small gold clusters derived from these fragments. Recently, Schmidbaur, a long-standing leader in the inorganic and organometallic chemistry of gold, has reviewed a number of aspects of the chemistry of gold that were directed by the isolobality concept.14 Similar to results for other transition metals, the organometallic chemistry and the catalytic properties of Au(I) complexes have been greatly enriched with the use of bulky 2e- donor ligands. Particularly important in this respect are Buchwald’s phosphines and other PR3-type 11 R. Hoffmann, Angew. Chem. Int. Ed. 1982, 21, 711-724. 12 F. G. A. Stone, Angew. Chem. Int. Ed. 1984, 23, 89-99 13 D. M. P. Mingos in Comprehensive Organometallic Chemistry I, Vol. 3. G. Wilkinson, F. G. A. Stone, E. W. Abel, Eds.; Pergamon: Oxford UK, 1982. 14 H. G. Raubenheimer, H. Schmidbaur, Organometallics 2012, 31, 2507-2522. Chapter I. Organometallic Compounds of Gold(I) Stabilized by Coordination to a Terphenylphosphine Ligand 32 ligands,15 as well as bulky Arduengo’s NHC and other cyclic carbenes.16 The latter are a type of molecules that resemble phosphines in their coordination properties (Figure 3). Figure 3. Buchwald’s phosphines and some cyclic carbenes. In recent years our research group has started a study of the organometallic chemistry of simple hydrocarbyl complexes of noble metals stabilized by bulky phosphine ligands, among them the terphenyl phosphine PMe2Ar’ shown in Figure 4 in which the terphenyl substituent on the phosphorous atom is the radical Ar’ = C6H3-2,6-(C6H3-2,6-Pri2)2 (in 15 For some important types of bulky phosphines used in organic catalytic processes mediated by transition metal complexes see: a) D. S. Surry, S. L. Buchwald, Chem. Sci. 2011, 2, 27-50; b) R. Martin, S. L. Buchwald, Acc. Chem. Res. 2008, 41, 1461-1473; c) R. J. Lundgren, M. Stradiotto, Aldrichimica Acta 2012, 45, 59-65; d) J. F. Hartwig, Acc. Chem. Res. 2008, 41, 1534-1544; e) G. C. Fu, Acc. Chem. Res. 2008, 41, 1555-1564; f) C. A. Fleckenstein, H. Plenio, Chem. Soc. Rev. 2010, 39, 694-711. 16 For some important types of NHC’s carbenes used in catalysis mediated by transition metal complexes see: a) H. Clavier, S. P. Nolan, Chem. Commun. 2010, 46, 841-861. For cyclic(alkyl)(amino)carbenes see: b) M. Soleilhavoup, G. Bertrand, Acc. Chem. Res. 2015, 48, 256-266. PR2 R' R' R = bulky substituent N RR NN RR R R R Chapter I. Organometallic Compounds of Gold(I) Stabilized by Coordination to a Terphenylphosphine Ligand 39 characterized by a Au—Cipso separation of 3.128(6) Å. This is significantly longer than the sum of the covalent radii (Csp2, 0.73; Au, 1.36 Å), but shorter than the sum of the van der Waals radii (ca. 4.09 Å).27 Figure 6. ORTEP view of complex 1; hydrogen atoms are excluded for clarity and thermal ellipsoids are set at 50% probability. Selected bond distances (Å) and angles (º): Au1—Cl1 = 2.300(2); Au1—P1 = 2.237(2); Au1—C7 = 3.128(6); P1—C1 = 1.848(5); P1—C31 = 1.829(5); P1—C32 = 1.825(5); P1-Au1-Cl1 = 175.41(6); C1-P1-Au1 = 117.8(2). I.3.1.2. Synthesis and Characterization of the Triflimide (NTf2; Tf = SO2CF3, 2) and Mesylate (Ms; Ms = SO3Me, 3) Analogues of Complex 1. As shown in Scheme 3, chloride abstraction from compound 1 with the silver salts AgNTf2 and AgMs, having the weakly coordinating anions 28, 795–801; d) E. Herrero-Gomez, C. Nieto-Oberhuber, S. Lopez, J. Benet-Buchholz, A. M. Echavarren, Angew. Chem. Int. Ed. 2006, 45, 5455-5459. 27 a) B. Cordero, V. Gómez, A. E. Platero-Prats, M. Revés, J. Echeverría, E. Cremades, F. Barragán, S. Álvarez, Dalton Trans. 2008, 2832-2838; b) S. Álvarez, Dalton Trans. 2013, 42, 8617–8636. Chapter I. Organometallic Compounds of Gold(I) Stabilized by Coordination to a Terphenylphosphine Ligand 40 triflimide and mesylate respectively, cleanly afforded the neutral species 2 and 3 that contain these anions bound to the cationic gold centre. Scheme 3. Synthesis of complexes 2 and 3. NMR spectra assignments for compounds 2 and 3 are collected in the Experimental Section and will not be discussed any further except to mention that the corresponding 31P{1H} resonances are shielded relative to the chloride precursor and appear at -11.5 and -13.4 ppm, respectively (- 5.7 ppm for complex 1). Complexes 2 and 3 were also characterized by single crystal X-ray diffraction, with the results summarized in Figures 7 and 8. As expected from the structure of the chloride complex 1 a weak interaction between Cipso and the gold centre was observed for the two compounds, with the corresponding distance in complex 3 being somewhat shorter (3.001(4) Å) than in 2 (3.134(2) Å). The Au—P bonds of the three complexes have similar lengths and are in the range of ca. 2.21-2.24 Å. AgNTf2 or AgMs CH2Cl2, 25 ˚C P iPr iPr iPr iPr Au Cl P iPr iPr iPr iPr Au X 1X = NTf2, 2; Ms, 3 Chapter I. Organometallic Compounds of Gold(I) Stabilized by Coordination to a Terphenylphosphine Ligand 41 Figure 7. ORTEP view of complex 2; hydrogen atoms are excluded for clarity and thermal ellipsoids are set at 50% probability. Selected bond distances (Å) and angles (º): Au1—P1 = 2.2366(8); Au1—N1 = 2.123(3); Au1—C23 = 3.134(2); P1—C5 = 1.839(2); N1—S1 = 1.627(2); N1—S2 = 1.630(3); Au1-P1-C5 = 120.61(9); P1-Au1-N1 = 167.57(7). Figure 8. ORTEP view of complex 3; hydrogen atoms are excluded for clarity and thermal ellipsoids are set at 50% probability. Selected bond distances (Å) and angles (º): Au1—P1 = 2.212(1); Au1—O1 = 2.082(3); Au1—C10 = 3.001(4); P1—C4 = 1.843(4); O1—S1 = 1.481(4); Au1-P1-C4 = 117.1(2); Au1-O1-S1 = 125.3(3); O1-Au1-P1 = 174.6(1). Chapter I. Organometallic Compounds of Gold(I) Stabilized by Coordination to a Terphenylphosphine Ligand 42 I.3.1.3. Cationic Adducts of Formula [Au(PMe2ArDipp2)(L)][NTf2] (L = NCMe, 4; THT, 5). These complexes were obtained by slightly different routes (Scheme 4). Thus, complex 4 was the result of the reaction of 1 with the acetonitrile adduct of the triflimide silver salt (CH2Cl2, 25 ºC), while the THT adduct 5 was cleanly obtained by treatment of complex [Au(NTf2)(PMe2ArDipp2)] (2) with THT (CH2Cl2, 25 ºC). The two adducts were completely characterized by NMR spectroscopy (see Experimental Section) and by single crystal X- ray diffraction studies (Figures 9 and 10). Interestingly, in these adducts there also seems to be a weak interaction between the gold center and a Cipso of the phosphine (Au1—C11 = 2.908(3) and Au1—C13 = 2.938(3) Å, in 4 and 5, respectively). Scheme 4. Synthesis of the adducts 4 and 5. CH2Cl2, 25 ˚C + NTf2- P iPr iPr iPr iPr Au S 5 AgNTf2·CH3CN CH2Cl2, 25 ˚C + NTf2- P iPr iPr iPr iPr Au NCMe 4 P iPr iPr iPr iPr Au Cl 1 i) AgNTf2 ii) THT Chapter I. Organometallic Compounds of Gold(I) Stabilized by Coordination to a Terphenylphosphine Ligand 43 Figure 9. ORTEP view of the cation of complex 4; hydrogen atoms are excluded for clarity and thermal ellipsoids are set at 50% probability. Selected bond distances (Å) and angles (º): Au1—P1 = 2.2277(7); Au1—N1 = 2.043(3); Au1— C11 = 2.908(3); P1—C5 = 1.834(3); N1—C1 = 1.103(4); C1—C2 = 1.465(5); Au1-P1-C5 = 114.78(9); Au1-N1-C1 = 174.9(3); P1-Au1-N1 = 175.19(8); N1- C1-C2 = 179.2(4). Figure 10. ORTEP view of the cation of complex 5; hydrogen atoms are excluded for clarity and thermal ellipsoids are set at 50% probability. Selected bond distances (Å) and angles (º): Au1-P1 = 2.2650(8); Au1-S1 = 2.3281(9); Au1-C13 = 2.938(3); S1-C1 = 1.845(5); S1-C4 = 1.827(4); C1-C2 = 1.513(6); C2-C3 = 1.513(8); C3-C4 = 1.504(7); Au1-P1-C7 = 115.8(1); P1-Au1-S1 = 176.39(3). Chapter I. Organometallic Compounds of Gold(I) Stabilized by Coordination to a Terphenylphosphine Ligand 44 I.3.1.4. Synthesis and Characterization of the Au(I) Hydrocarbyl Complexes [Au(R)(PMe2ArDipp2)] (R = Me, 6a; Et, 6b; CH2CMe2Ph, 6c; Ph, 6d; CH=CH2, 6e; C≡CH, 6f). Compound 1 is a suitable precursor for the synthesis of the hydrocarbyl derivatives 6a-6f by its reaction with solutions of the appropriate organometallic transfer reagents. For alkyl complexes 6a and 6b the corresponding ZnR2 alkylating agents were chosen while LiC6H5 was employed for the preparation of 6d. In turn, the Grignard reagents Mg(R)X (X = Cl, Br) were utilized to reach the neophyl complex 6c, as well as the ethenyl and ethynyl derivatives 6e and 6f. All reactions were performed in toluene at -40 ºC, as summarized in Scheme 5, and provided the new organogold complexes in good isolated yields (close to 60 %). Scheme 5. Synthesis of the Au(I) hydrocarbyl complexes 6a-6f. To minimize reduction of the Au(I) precursor to metallic gold by action of the organometallic transfer reagent (the reduction power of which 1 P iPr iPr iPr iPr Au Cl P iPr iPr iPr iPr Au R 6a, R = Me 6b, R = Et 6c, R = CH2CMe2Ph 6d, R = Ph 6e, R = CH=CH2 6f, R = C CH ZnR2, or RLi, or Mg(R)X, toluene, -40 ˚C Chapter I. Organometallic Compounds of Gold(I) Stabilized by Coordination to a Terphenylphosphine Ligand 45 changes in the order LiR > Mg(R)X > ZnR2), the solution of the transfer reagent was added dropwise to complex 1, in toluene, at -40 ºC. It is interesting to note that a clean, unexpected exchange process was observed in the reaction leading to the acetylide complexe 6f when the transfer reagent was the bromide of the acetylide Grignard reagent and the reaction mixture was allowed to warm to room temperature. Under these conditions a clean metathesis reaction occurred that converted acetylide complex 6f into the corresponding bromide 1·Br, as depicted in Scheme 6. To avoid the formation of the latter, work up of the reaction was carried out at low temperature (-20 ºC). Complex 7 was completely characterized by the usual techniques, including single crystal X-ray diffraction (Figure 11). Once again, a weak interaction between the gold atom and a Cipso of the phosphine was ascertained, characterized by a Au1···C7 contact of 3.116(3) Å. Scheme 6. Synthesis of the alkynyl complex 6f, and its room temperature transformation into complex 1·Br (when work-up of the reaction mixture was carried out at 25 ºC instead of at -20 ºC). 1·Br P iPr iPr iPr iPr Au Br 1 P iPr iPr iPr iPr Au Cl P iPr iPr iPr iPr Au C 6f Mg(C toluene, -40 ˚C toluene, without isolation of 6f CH)Br CH -40 to 25 ˚C Chapter I. Organometallic Compounds of Gold(I) Stabilized by Coordination to a Terphenylphosphine Ligand 46 Figure 11. ORTEP view of complex 1·Br; hydrogen atoms are excluded for clarity and thermal ellipsoids are set at 50% probability. Selected bond distances (Å) and angles (º): Au1—Br1 = 2.4107(5); Au1—P1 = 2.2412(8); Au1—C7 = 3.116(3); P1—C1 = 1.846(3); P1-Au1-Br1 = 174.96(2); Au1-P1-C1 = 117.52(8). I.3.1.4.1. Nuclear Magnetic Resonance Spectra of Complexes 6a-6f. Complexes 6a-6f have been completely characterized by microanalysis and NMR spectroscopy. In a similar fashion to complex 1, these hydrocarbyl species experience free rotation on the NMR time scale at 25 ºC around the P—C and Car—Car bonds of the phosphine, as unequivocally deduced from their 1H and 13C{1H} NMR spectra. As expected, the 31P{1H} NMR spectrum of complexes 6a-6f is a singlet and appears significantly deshielded in comparison with the chloride precursor 1 (-5.7 ppm). The δ range spans from 7.1 (6f) to 19.5 ppm (6b). In fact, the three alkyl derivatives have very similar chemical shift values (in the interval 18.8-19.5 ppm; see Experimental Section). The 1H and 13C{1H} Chapter I. Organometallic Compounds of Gold(I) Stabilized by Coordination to a Terphenylphosphine Ligand 47 NMR spectra of the methyl, ethyl, neophyl 28 and phenyl21b,28a, 29 compounds are also very simple and will not be analyzed in detail. Suffice to mention that the Au-CH2R linkage of complexes 6a-6c is responsible for strongly shielded 1H NMR resonances (-0.35 for 6a; 0.48, 6b; and 0.94 ppm, 6c) that exhibit three-bond 1H-31P couplings of roughly 8-9 Hz. The corresponding 13C{1H} signals have divergent chemical shifts (5.0, 6a; 19.8, 6b and 50.8 ppm, 6c), but similar 2JCP coupling constants of approximately 100-105 Hz. Interestingly, in the phenyl complex 6d, the gold-bonded carbon atom resonates at 171.2 ppm and has a coupling constant 2JCP of 123 Hz, in agreement with the experimental data found in the literature for somewhat related compounds.30 28 For some selected examples see: a) M. T. Johnson, J. Marthinus Janse van Rensburg, M. Axelsson, M. S. G. Ahlquist, O. F. Wendt, Chem. Sci. 2011, 2, 2373; b) V. J. Scott, J. A. Labinger, J. E. Bercaw, Organometallics 2010, 29, 4090-4096. 29 For some selected examples see: D. V. Partyka, J. B. Updegraff III, M. Zeller, A. D. Hunter, T. G. Gray, Organometallics 2009, 28, 1666–1674. 30 S. Gaillard, A. M. Z. Slawin, S. P. Nolan, Chem. Commun. 2010, 46, 2742-2744. Chapter I. Organometallic Compounds of Gold(I) Stabilized by Coordination to a Terphenylphosphine Ligand 48 Figure 12. 1H NMR spectra of complexes 6b-6c and 6d-6e (400 MHz, CD2Cl2, 25 ºC). Figure 12 compares the room temperature 1H NMR spectra (between ca. 7.6 and 0.4 ppm) of complexes 6b, 6c, 6e and 6f. The vinyl terminus of 6e is characterized by three multiplets, each a doublet of doublet of doublets, that appear at 6.37 (3JHH = 20.2, 3JHH = 13.8, 3JHP = 6.0 Hz; CH=CH2), 5.57 (3JHH = 13.8, 2JHH = 5.4, 4JHP = 19.3 Hz; CH=CHHcis, cis respect to the methyne proton) and 4.96 ppm (3JHH = 20.6, 2JHH = 5.3, 4JHP Chapter I. Organometallic Compounds of Gold(I) Stabilized by Coordination to a Terphenylphosphine Ligand 55 the proximal Dipp substituents. The interactions must be very weak, as hinted by the lengths of the observed contacts, that amount 3.222(8) and 3.127(2) Å, for 6e and 6f, respectively. It is also of note that while they present normal Au—Csp2 and Au—Csp bonds with lengths 2.05(1) and 2.029(4) Å, respectively, they exhibit unusually short C—C bond distances for the coordinated hydrocarbyl ligand, with values of 1.224(16) and 1.116(5) Å for the –CH=CH2 and –C≡CH termini, respectively. These bond lengths are significantly shorter than in the free hydrocarbons (1.34 and 1.20 Å in C2H4 and C2H2, respectively). Although Au(I)(PR3) fragments usually have high electrophilicity and low capacity for backdonation,35 the above observations are difficult to explain. They are not, however, unique as revealed by the histograms represented in Figures 18 and 19. Complex 6e is the only Au-CH=CH2 complex that has been reported in the literature and features the shortest C—C bond length found for gold alkenyls (Figure 18), but there is a significant number of examples with C=C bond lengths of ca. ≤ 1.34 Å.36 With reference to alkynyl 6f, two other acetylides [Au(C≡CH)(PR3)] complexes have been characterized by X-ray crystallography and possess C≡C bond lengths of 1.171(9) and 35 a) G. Seidel, A. Fürstner, Angew. Chem. Int. Ed. 2014, 53, 4807-4811; b) R. E. Brooner, R. A. Widenhoefer, Chem. Commun. 2014, 50, 2420-2423; c) H. Willner, F. Aubke, Chem. Eur. J. 2003, 9, 1668–1676. 36 For substituted vinyls of this kind, see: a) D. Weber, M. A. Tarselli, M. R. Gagné, Angew. Chem. Int. Ed. 2009, 48, 5733-5736; b) A. S. K. Hashmi, T. D. Ramamurthi, F. Rominger, J. Organomet. Chem. 2009, 694, 592-597; c) Y. Shi, S. D. Ramgren, S. A. Blum, Organometallics 2009, 28, 1275–1277; d) F. Mohr, L. R. Falvello, M. Laguna, Eur. J. Inorg. Chem. 2006, 2006, 833-838. Chapter I. Organometallic Compounds of Gold(I) Stabilized by Coordination to a Terphenylphosphine Ligand 56 1.187(6) Å.31 The latter distances are significantly longer than in complex 6f (1.116(6) Å) but they are also slightly smaller than in free acetylene. It is difficult to provide a rational for these observations. Computational studies from Dr. Wen-Hua Xu and Prof. Pekka Pyykkö on C2H2 and model complex [Au(C≡CH)(PH3)] indicate a slight lengthening of the C—C bond, from ca. 1.22 Å (computed value for C2H2) to about 1.234 Å in the gold complex,37 and not a shortening. The possibility exists that the diffraction experiment gives a distorted result due to an unforeseen disorder problem, similar for example to that responsible for the long controversy on the existence of “bond-stretch isomerism” for cis-mer- [Mo(O)Cl2(PR3)] complexes. 38 Notwithstanding the aforementioned possibility, we decided to concentrate efforts on further developing the chemistry of these complexes, rather than on the above structural observation, or apparent observation. Leaving aside these unresolved structural aspects, it is pertinent to accentuate the chemical significance of complexes 6e and 6f, the prototypes for gold alkenyl and alkynyl species. Such complexes and related digold cationic species thereof, are commonly accepted intermediates in many gold-catalyzed C—C bond forming reactions of alkenes, alkynes, allenes and other unsaturated organic molecules.2 Their 37 Professor P. Pyykkö, personal communication to Prof. E. Carmona. 38 a) K. Yoon, G. Parkin, A. L. Rheingold, J. Am. Chem. Soc. 1992, 114, 2210–2218; b) G. Parkin, Chem. Rev. 1993, 93, 887-911. Chapter I. Organometallic Compounds of Gold(I) Stabilized by Coordination to a Terphenylphosphine Ligand 57 relevance will be re-emphasized later, in forthcoming sections of this Thesis (I.3.2.3 and I.3.2.4). Figure 18. Histograms of the C=C (left) and C—Au (right) bond distance distribution in Au>C=C< complexes according to the CSD. Values of the corresponding distances for complex 6e are marked with a red arrow. Chapter I. Organometallic Compounds of Gold(I) Stabilized by Coordination to a Terphenylphosphine Ligand 58 Figure 19. Histograms of the C≡C (left) and C—Au (right) bond distance distribution in Au-C≡C- complexes according to the CSD. Values of the corresponding distances for complex 6f are marked with a red arrow. I.3.2. Cationic Hydrocarbyl-Bridged Digold(I) Complexes of Formula [Au2(µ2-R)(PMe2ArDipp2)2][NTf2] (R = Me, 7a; Et, 7b; CH2CMe2Ph, 7c; Ph, 9; CH=CH2, 10; C≡CH, 11). This section is devoted to the study of binuclear complexes of Au(I) that can accurately be viewed as resulting from coordination of the neutral hydrocarbyls [Au(R)(PMe2ArDipp2] (6a-6f), described in the previous paragraphs to the highly electrophilic cation [Au(PMe2ArDipp2)]+. As discussed next, the two gold cantres are bound together through the bridging hydrocarbyl group and experience additional stabilization by virtue of aurophilic interactions. Having in mind the divergent electronic Chapter I. Organometallic Compounds of Gold(I) Stabilized by Coordination to a Terphenylphosphine Ligand 59 and structural characteristics of the Au(µ2-R)Au bridges in the resulting complexes, 7a-7e, it is pertinent to organize them into three subgroups, comprising respectively the alkyl-bridged derivatives 7a-7c, the phenyl complex 9, and the vinyl and acetylide species 10 and 11. All new compounds were isolated as triflimide salts, [Au2(µ2- R)(PMe2ArDipp2][NTf2], and were characterized by X-ray crystallography, with the exception of the thermally unstable alkyls 7b and 7c. I.3.2.1. Synthesis and Characterization of the Cationic gem-σ,σ-Diaurated Alkyl Complexes [Au2(µ- R)(PMe2ArDipp2)][NTf2] (R = Me, 7a; Et, 7b; C2H2CMe2Ph, 7c). The, in our view highly interesting, dinuclear cationic complex 7a, having a methyl group that symmetrically bridges two gold atoms20 (Scheme 7), was first observed as the unexpected product of the room temperature reaction of complex 7a with the strong Brönsted acid HBArF. Originally, this reaction was aimed at the generation of the unsaturated species, I, that could be stabilized by a secondary Au···Carene interaction or by coordination of CH2Cl2. Most likely, this stabilization took place, but the [Au(PMe2ArDipp2)]+ cation preferred to stabilize itself by, a kineticallycontrolled coordination to a molecule of the starting material, with formation of the symmetrical methyl-bridged complex 7a. Therefore, the latter species stemmed from the two-step process depicted in Scheme 7. Chapter I. Organometallic Compounds of Gold(I) Stabilized by Coordination to a Terphenylphosphine Ligand 60 Scheme 7. Synthesis of the gem-diaurated methyl species 7a by reaction of complex 6a with the strong acid HBArF. The unsaturated species I acts as a highly reactive intermediate. It is worth remarking that since a 1:1 ratio of the 6a and HBArF reagents was employed, the initially generated [Au(PMe2ArDipp2)]+ cation competed successfully with H+ for the trapping of still unreacted amounts of the [Au(Me)(PMe2ArDipp2)] precursor, leaving unreacted half the quantity of the acid added for the protonation reaction. In accordance with these arguments it was foreseen that complex 7a could also be generated by the reaction of equimolar amounts of compounds [Au(Me)(PMe2ArDipp2)] (6a), and [Au(NTf2)(PMe2ArDipp2)] (2). In fact, this method constitutes a well-known, successful route for the synthesis of related cationic gem-diaurated hydrocarbyl species.22d,28b,34,39 Our goal was readily accomplished so that this procedure (CH2Cl2, -80 ºC to 25 ºC) was applied successfully (Scheme 8) for the preparation of the related ethyl and neophyl complexes 7b and 7c, respectively. NMR monitoring (CD2Cl2) of the formation of the dinuclear complexes indicated that the reactions took place at temperatures as low as -80 ºC. Interest in 39 Y. Tang, J. Li, Y. Zhu, Y. Li, B. Yu, J. Am. Chem. Soc. 2013, 135, 18396-18405. Au Au + Me PP iPr iPr iPr iPr iPr iPr iPr iPr P iPr iPr iPr iPr Au Me P iPr iPr iPr iPr Au + BArF- HBArF CH2Cl2, 25 ºC + 6a CH2Cl2, 25 ºC I (not observed) 6a 7a Chapter I. Organometallic Compounds of Gold(I) Stabilized by Coordination to a Terphenylphosphine Ligand 61 compounds of this kind that possess a [Au2(µ-R)]+ core where R = alkenyl or acetylide bridging groups, has increased tremendously in recent years due to their proposed participation in many catalytic processes that involve unsaturated organic molecules.2 Remarkably, analogous complexes with bridging alkyl groups were unknown until the present work. Scheme 8. Synthesis of the gem-σ,σ-diaurated alkyl compounds 7a-7c. Unpublished work from our group19,40 has allowed the synthesis of other [Au(µ-Me)Au]+ complexes stabilized by different terphenylphosphines, among them the 2,6-Me2C6H3-substituted PMe2ArXyl2. Complex 7a is considerably more stable than the [Au2(µ- Me)(PMe2ArXyl2)2]+ analogue, as the latter decomposed at temperatures ≥ - 20 ºC and could only be characterized by low-temperature NMR spectroscopy. Clearly, the 2,6-Pri2C6H3 flanking aryl rings of PMe2ArDipp2 provide more efficient steric protection to the [Au(µ-Me)Au]+ central unit 40 This complex was only characterized by NMR spectroscopy at -20 ºC (CD2Cl2). Its decomposition is a second order reaction. Jesús Campos, unpublished work. P iPr iPr iPr iPr Au R 6a, R = Me 6b, R = Et 6c, R = CH2C(Me)2Ph 2 + Au Au + RNTf2- PP iPr iPr iPr iPr iPr iPr iPr iPr CH2Cl2 - 80 to 25 ˚C 7a, R = Me 7b, R = Et 7c, R = CH2C(Me)2Ph P iPr iPr iPr iPr Au NTf2 Chapter I. Organometallic Compounds of Gold(I) Stabilized by Coordination to a Terphenylphosphine Ligand 62 of 7a than the 2,6-Me2C6H3 substituent in the related PMe2ArXyl2 complex. For complex 7a, the bridging methyl group gives rise at room temperature to a 1H resonance at 0.34 ppm, while the corresponding 13C nucleus resonates at -0.1 (t, 2JCP = 53; 1JCH = 129 Hz). In accordance with the proposed symmetry for the cation of 7a, the coupling constants between the carbon-13 nucleus of the methyl group and the two phosphorous nuclei are equal and their value is almost half the magnitude found for the mononuclear complex 3a (2JCP = 102 Hz). Besides, the 1JCH for the bridging methyl is in accord with this group being symmetrically bonded to the two Au centres without agostic C⎯H···Au bonds. In the 31P{1H} NMR, the two phosphorous nuclei are equivalent and appear as a singlet at -0.2 ppm. Complex 7a was characterized by single crystal X-ray diffraction, and its structure is shown in Figure 20. This study supports the main conclusions derived from the NMR analysis just discussed. But it shows in addition that the two gold atoms bind to the methyl carbon almost symmetrically (2.210(6) and 2.225(5) Å) and experience the expected Au···Au bonding interaction with a distance between the two gold atoms of 2.7122(2) Å. This separation is significantly shorter than the average of distances found in other non-alkyl gem-digold species (ca. 2.90 Å).21 Moreover, the Au···Au separation in 7a is also shorter than the value of 2.878 Å found for the metallic gold.41 Similar to the majority of the complexes reported in this work, two Au−Cipso stabilizing interactions 41 J. K. Burdett, O. Eisenstein, W. B. Schweizer, Inorg. Chem. 1994, 33, 3261–3268. Chapter I. Organometallic Compounds of Gold(I) Stabilized by Coordination to a Terphenylphosphine Ligand 63 between the gold atoms and respective flanking aryl rings are also evident in complex 7a, with Au···Carene separations of 3.03 and 3.10 Å (Figure 20). Before proceeding any further, it is important to recall that complex 7a is the first example of a digold [Au2(µ-R)]+ complex that possesses a methyl bridge. The simple model complex [(H3P)Au(CH3)Au(PH3)]+ was studied theoretically in 1994, with a fixed Au—Au distance of 2.82 Å.41 Figure 20. ORTEP view of the cation of complex 7a; hydrogen atoms are excluded for clarity and thermal ellipsoids are set at 50% probability. Selected bond distances (Å) and angles (º): Au1—Au2 = 2.7120(8); Au1—C33 = 2.210(5); Au2—C33 = 2.227(4); Au1—P1 = 2.259(1); Au2—P2 = 2.262(1); Au1—C7 = 3.102(4); Au2—C52 = 3.027(3); Au1-C33-Au2 = 75.4(1); Au1-Au2-C33 = 52.0(1); Au2-Au1-C33 = 52.6(1); Au1-Au2-P2 = 133.52(4); Au2-Au1-P1 = 132.79(4); P1-Au1-C33 = 172.4(1); P2-Au2-C33 = 172.4(1); Au1-P1-C1 = 118.5(1); Au2-P2-C34 = 118.6(1). Chapter I. Organometallic Compounds of Gold(I) Stabilized by Coordination to a Terphenylphosphine Ligand 64 As noted briefly (see the Introduction, page 4 and Figure 2) the species Au(PR3)+ is isolobal with H+. This analogy, Au(PR3)+ H+, or the equivalent between the respective neutral species, ·Au(PR3) ·H, have been used widely in organometallic chemistry and allows the view of the pentagold “carbide” {C[(Ph3P)Au]5}+ as isolobal to CH5+, i.e. protonated methane,8,9 a molecule postulated nearly fifty years ago by Olah to understand certain NMR features of solutions of CH4 in strongly acidic media.10 Similarly, complex 7a may be considered as consisting of [(ArDipp2Me2P)Au(CH3)] and [Au(PMe2ArDipp2)]+ fragments, and viewed, once more, as isolobal to CH5+. But from a slightly different perspective, [(ArDipp2Me2P)Au(CH3)] is isolobal to methane, CH4, which leads to an image of compound 7a as a cationic gold(I) methane complex. We also thought it of interest (vide supra) to prepare similar complexes with ethyl (-CH2CH3) and neophyl (-CH2CMe2Ph) bridges (Scheme 8). The first has β-H atoms whereas the second is void of such atoms. Experimentally it was found that both complexes exhibit considerably reduced thermal stability in comparison with the parent complex 7a. Of the two, ethyl complex 7b is stable in solution below -10 ºC for extended periods of time (at least 12 hours), while 7c decomposes after only two hours at -20 ºC. The moderate stability of 7b permitted NMR characterization at -10 ºC in CD2Cl2 solution overnight. The 1H and 13C{1H} NMR spectra of complex 7b are shown in Figure 21. The bridging ethyl group is characterized by two high-field 1H multiplets at 1.12 and 0.85 ppm, corresponding to the methylene and Chapter I. Organometallic Compounds of Gold(I) Stabilized by Coordination to a Terphenylphosphine Ligand 71 bond distances and angles. In marked contrast with the nearly symmetrical coordination disclosed for the [Au2(µ-Me)]+ complex 7a, where the two Au-(µ-CH3)-Au bonds are practically identical (2.227(4) and 2.210(5) Å), the binding of the vinyl carbon atom that is connected to the two gold centres is noticeably non-symmetrical, with Au—C distances of 2.066(9) and 2.210(8) Å (Au1—C1 and Au2—C1, respectively). The former is comparable to the Au—C distance in the parent vinyl complex 6e, and significantly shorter than the already mentioned Au—CH3 contacts in the bridging methyl derivative 7a, which is not unexpected in view of the different hybridizations of the bridging carbon atoms and of the diverse directional properties of the hybrid orbitals. In turn, the Au2—C1 separation (2.210(8) Å) is almost identical to the Au—C distances in the methyl-bridged complex 7a. Chapter I. Organometallic Compounds of Gold(I) Stabilized by Coordination to a Terphenylphosphine Ligand 72 Figure 22. ORTEP view of the cation of complex 10; hydrogen atoms are excluded for clarity and thermal ellipsoids are set at 50% probability. Selected bond distances (Å) and angles (º): Au1—Au2 = 3.0737(4); Au1—P1 = 2.297(2); Au1—C1 = 2.066(9); Au1—C23 = 3.077(9); Au2—P2 = 2.261(2); Au2—C1 = 2.210(8); Au2—C2 = 2.34(1); Au2—C43 = 3.069(8); C1—C2 = 1.28(2); Au1- Au2-C1 = 42.2(3); Au1-C1-Au2 = 91.9(4); Au1-C1-C2 = 128.6(8); Au1-Au2-P2 = 130.02(6); Au2-Au1-C1 = 45.9(3); Au2-Au1-P1 = 128.20(5); P1-Au1-C1 = 170.7(3); P2-Au2-C1 = 171.9(3); P2-Au2-C2 = 149.7(3). But the most relevant structural feature of ethenyl complex 10 is doubtless the η2-alkene coordination of the Au1-C1=C2 carbon-carbon double bond to the other gold atom, Au2, evidenced by a relatively short bond between Au2 and the other olefinic carbon atom, C2, of length 2.34(1) Å. For comparative purposes, in the isobutene complex [Au(CH2=CMe2)(PBut3)]+, the gold atom features also η2-coordination, with Au—CH2 and Au—CMe2 distances of 2.224(9) and 2.350(8) Å, and it is therefore slightly slipped toward the less-substituted carbon atom.2a Chapter I. Organometallic Compounds of Gold(I) Stabilized by Coordination to a Terphenylphosphine Ligand 73 These distances are similar to those in 10 but show an opposite trend, as in the latter the shorter Au—C bond corresponds to the Au-substituted carbon atom C1, probably as a consequence of the existence of a weak aurophilic interaction (3.074(4) Å). It is, however, of note, that this Au1···Au2 contact is ca. 0.3 Å longer than in the methyl-bridged complex 7a, probably as a result of a bonding compromise for Au2 between the aurophilic interaction and bonding to the C1=C2 bond. These structural and bonding peculiarities will be discussed later in sufficient detail. The C1=C2 bond lengthens upon complexation to 1.28(2) Å (1.224(16) Å in 6e) but remains shorter than in free ethylene (1.34 Å). In the isobutylene complex referenced above, 2a, the coordinated C=C bond is also short (ca. 1.35 Å), albeit longer than in 10. To complete this structural discussion, it should be mentioned that each Au atom participates in a weak Au···Carene interaction (ca. 3.07 Å; see Figure 22). In our view, the structure of complex 10 is important for several reasons. Firstly, even if other alkenyl-bridged [Au2L2]+ complexes have been structurally characterized (vide infra) it is the first vinyl digold complex to be reported. In addition, as mentioned briefly, 10 may be considered as a complex of the gold cation [Au(PMe2ArDipp2)]+ and the gold-substituted alkene CH2=C(H)-Au(PMe2ArDipp2). Besides, complex 10 is doubtless a most appropriate model for the isolobal protonated ethylene species, viz. cation C2H5+. There is now theoretical consensus that similar Chapter I. Organometallic Compounds of Gold(I) Stabilized by Coordination to a Terphenylphosphine Ligand 74 to 10, the proton in C2H5+ interacts symmetrically with the π component of the carbon-carbon bond.47 Figure 23 contains structural representations of the few alkenyl complexes that have been characterized by X-ray crystallography, including compound 10. Some solution 13C{1H} NMR data are also given. As can be seen, there is only one example that, in analogy with 10, contains a σ,π-alkenyl bridge. The complex holds (NHC)Au fragments and was formed when a fluoride-bridged digold compound added across an allene C=C bond. The crystal structure exhibited, however, substantial disorder that affected the Au atoms and could not be resolved, although it provided insights into the binding mode of the alkenyl ligand.21a The remaining structures feature a σ,σ-type bridge and contain a substituted terminal carbon atom. It is therefore tempting to speculate that such substitution hinders η2-olefin coordination, although insufficient examples are available for a generalization of this kind to be made. 47 A. M. Ricks, G. E. Douberly, P. v. R. Schleyer, M. A. Duncan, Chem. Phys. Lett. 2009, 480, 17-20. Chapter I. Organometallic Compounds of Gold(I) Stabilized by Coordination to a Terphenylphosphine Ligand 75 Figure 23. Solid state structures of substituted alkenyl-bridged complexes previously characterized by X-ray crystallography and their corresponding 13C{1H} NMR solution data. Complex 10 has been included for comparative purposes. Figure 24 shows the 1H NMR spectrum (500 MHz, CD2Cl2, 25 ºC) of complex 10. The bridging vinyl ligand is responsible for three multiplets Au Au H H CMe2F + Au Au Ph3PPPh3 H H + NTf2- N NN N ArDipp2 ArDipp2ArDipp2 ArDipp2 BF4- Au Au H Ph H+ BF4- N NN N ArDipp2 ArDipp2ArDipp2 ArDipp2 (Sadighi, 2014) (Fürstner, 2010) (Nolan, 2013) Au Au Ph3PPPh3 Me OEt H + NTf2- (Fürstner, 2010) 184.5 140.7 122.6 168.5 134.4 128.5 192.2 174.8 3JCP = 2 Hz 2JCP = 14 Hz 2JCP no reported 3JCP = 0 Hz 3.18 Å2.82 Å 2.80 Å2.76 Å Au Au H H CMe2F Ar'Me2PPMe2Ar' 10 154.0 2JCP = 60 142.2 2JCP 0 3.07 Å (Ar' = PMe2ArDipp2) + NTf2- Chapter I. Organometallic Compounds of Gold(I) Stabilized by Coordination to a Terphenylphosphine Ligand 76 at 5.41 (dtd, 3JHH = 13.0, 3JHP = 6.3, 2JHH = 4.4 Hz, CH=CHfHg), 5.29 (ddt, 3JHH = 20.3, 2JHH = 4.4, 3JHP = 1.5 Hz, CH=CHfHg) and 4.80 ppm (ddt, 3JHH = 20.4, 2JHH = 13.0, 3JHP = 1.5 Hz, CHe=CH2). The corresponding carbon-13 nuclei resonate with δ 142.2 (CH=CH2) and 154.0 (t, 3JCP = 60 Hz, CH=CH2). When these chemical shift and coupling constant values are compared with those of the vinyl ligand in the mononuclear precursor, 6e, at 128.4 ppm (3JCP ≈ 0 Hz, CH=CH2) and 168.4 (2JCP = 125 Hz, CH=CH2), it becomes clear that the chemical shifts of the two olefinic carbon atoms in 10 are now more similar, with the α carbon being deshielded by roughly the same magnitude (Δδ ≈ 14 ppm) than the β carbon is shielded. Comparison of these 13C NMR parameters with those reported in the literature for the complexes collected in Figure 23 reveals that, unfortunately, they are of little use to discriminate between σ,σ- and σ,πalkenyl binding modes. Finally, the 2JCP value in the digold complex 10 is approximately half its magnitude in the mononuclear species 6e. A similar phenomenon was noted for the alkyl complexes described previously. Chapter I. Organometallic Compounds of Gold(I) Stabilized by Coordination to a Terphenylphosphine Ligand 77 Figure 24. 1H NMR spectrum (500 MHz, CD2Cl2, 25 ºC) of complex 10. The two phosphorous nuclei in 10 are equivalent at 25 ºC (δ = 0.24 ppm, CD2Cl2), and remained isochronous at -60 ºC. This behaviour, along with the fact that the α carbon atom of the vinyl group presents identical 13C-31P couplings to the two phosphines, indicate unambiguously the highly fluxional nature of this species that undergoes fast exchange of the two gold centres in the NMR time scale, even at -60 ºC. A plausible mechanism for this exchange process is shown in Scheme 12, where the σ,σ-CH=CH2 structure G is proposed as an intermediate or a transition state. This mechanism converts 10 into its enantiomer and it has already Chapter I. Organometallic Compounds of Gold(I) Stabilized by Coordination to a Terphenylphosphine Ligand 78 been advanced for other structurally characterized σ,π-substituted vinyl complexes.21a,22f Scheme 12. Fluxional behavior of complex 10 (CD2Cl2, -60 ºC) and proposed mechanism for the observed exchange. I.3.2.4. The Acetylide Complex Analogue of 10. Synthesis, Solution and Solid-State Molecular Structure of the Cationic gem-σ,π-Diaurated Complex [Au2(µ2-C≡CH)(PMe2ArDipp2)][NTf2] (11). Cationic gold(I) alkyne compounds of the type [Au(η2-alkyne)L]+ are scarce, even if they are widely proposed as intermediates in the homogeneous catalytic activation of the carbon-carbon triple bond towards nucleophilic attack. In 2010, following their successful synthesis of [Au(η2-alkene)(PBut3)][SbF6] alkene complexes cited in the previous section,44a Hooper, Green and Russell provided the first structural evidence for the related alkyne derivatives [Au(η2-RC≡CR’)(PBut3)][SbF6] for the 10 Au Au H H H LL + NTf2- L = PMe2ArDipp2 Au Au LL H H H Au Au H H LL + NTf2- H ent-10 + NTf2- G Chapter I. Organometallic Compounds of Gold(I) Stabilized by Coordination to a Terphenylphosphine Ligand 79 alkynes MeC≡CBut and Me3SiC≡CBut.22f Shortly afterwards, other complexes of this kind were reported.22b,48 Interestingly, coordination of a terminal alkyne to the electrophilic gold(I) centre enhances the acidity of the acetylene proton facilitating the formation of an acetylide. In fact, Bertrand described the isolation of a Au(I) η2-PhC≡CH complex and its conversion to the corresponding σacetylide upon treatment with Et2NH.49 Later, Widenhoefer demonstrated that cationic Au(I) complexes of arylacetylenes generated at low temperatures, experienced at -20 ºC spontaneous C—H bond cleavage and nucleation to form stable gem-σ,π-diaurated complexes. One of these compounds was characterized by X-ray crystallography.48b In analogy with the results reported in section I.3.2.3 for the vinyl complex 6e, we carried out the reaction of the acetylide complex 6f with [Au(NTf2)(PMe2ArDipp2)] (2), as the source of the [Au(PMe2ArDipp2)]+ cation, to obtain in yields close to 90% the expected binuclear gemdiaurated σ,π-acetylide species 11 (Scheme 13). Digold complexes of this type seem not to be active in the course of Au(I) catalyzed reactions of alkynes and to behave more as inactive end-products2 that may become activated in some cases under special chemical conditions. Although 48 See for example: a) A. Himmelspach, M. Finze, S. Raub, Angew. Chem. Int. Ed. 2011, 50, 2628-2631; b) T. J. Brown, R. A. Widenhoefer, Organometallics 2011, 30, 6003−6009; c) A. Das, C. Dash, M. A. Celik, M. Yousufuddin, G. Frenking, H. V. R. Dias, Organometallics 2013, 32, 3135-3144; d) A. S. Hashmi, T. Lauterbach, P. Nosel, M. H. Vilhelmsen, M. Rudolph, F. Rominger, Chem. Eur. J. 2013, 19, 1058-1065. 49 V. Lavallo, G. D. Frey, S. Kousar, B. Donnadieu, G. Bertrand, PNAS 2007, 104, 13569- 13573. Chapter I. Organometallic Compounds of Gold(I) Stabilized by Coordination to a Terphenylphosphine Ligand 80 several examples have been structurally characterized,22 complex 11 is the only representative that derives from the parent alkyne C2H2. Scheme 13. Synthesis of σ,π-acetylide bridged compound 11. Figure 25 shows an ORTEP perspective view of the molecules of 11. Once more, the α carbon atom of the hydrocarbyl ligand (C1) binds to the two gold(I) centres in a non-symmetrical manner, with one short bond (to Au1, 2.003(8) Å) and a longer one (to Au2, 2.245(8) Å), in accordance with the proposed σ,π-coordination of the acetylide moiety. The η2-alkyne interaction features a second gold-carbon contact (Au2—C2) of identical length within error (2.23(1) Å). The C≡C bond distance of 1.19(1) Å is identical within the error of the experiment to that in acetylene (1.20 Å), but it is slightly longer than in the neutral acetylide 6f (1.116(6) Å). As in other [Au(µ-R)Au]+ complexes already discussed, each gold atom participates in a stabilizing Au···Cipso interaction with a flanking aryl ring of its P-bonded terphenylphosphine ligand (2.94 and 2.99 Å, approximately). Au Au H PP iPr iPr iPr iPr iPr iPr iPr iPr 11 + CH2Cl2 - 80 ˚C to 20 ˚C + NTf2 - 6f P iPr iPr iPr iPr Au C CH 2 P iPr iPr iPr iPr Au NTf2 Chapter I. Organometallic Compounds of Gold(I) Stabilized by Coordination to a Terphenylphosphine Ligand 87 Figure 27. 1H NMR spectrum (500 MHz, CD2Cl2, 25 ºC) of complex 11 and a schematic comparison of the 13C NMR data of this species with those of the mononuclear compound 6e. Variable temperature 31P{1H} and 13C{1H} studies of this complex disclosed properties similar to those already commented for the vinyl derivative 10. As expected, acetylide 11 is highly fluxional in solution (CD2Cl2) and the exchange represented in Scheme 14 occurs very fast in the NMR time scale, even at -60 ºC. This behaviour is also apparent in other related acetylides and the mechanism proposed for the exchange in Scheme 14 was already anticipated in the literature.21a,22f Chapter I. Organometallic Compounds of Gold(I) Stabilized by Coordination to a Terphenylphosphine Ligand 88 Scheme 14. Fluxional behaviour of complex 11 (CD2Cl2, -60 ºC) and proposed mechanism for the exchange observed. In conclusion, with the synthesis and structural characterization of the cationic methyl-bridged complex 7a, an important gap in the organometallic chemistry of Au(I) has been filled. This compound, and the related vinyl and acetylide complexes 10 and 11, respectively, form the simplest series available of isolable organometallic [Au(µ-R)Au]+ derivatives, and offer the opportunity of determining experimentally the variation in the strength of the aurophilic interaction that accompanies a change in the hybridization of the bridging carbon atom. Au Au H LL 11 + NTf2- Au Au C LL C+ NTf2- Au Au H LL ent-11 + NTf2- H H L = PMe2ArDipp2 Chapter I. Organometallic Compounds of Gold(I) Stabilized by Coordination to a Terphenylphosphine Ligand 89 II.4. EXPERIMENTAL SECTION II.4.1. General Considerations. All operations were performed under a nitrogen atmosphere using standard Schlenk techniques, employing dry solvents and glassware. HRMS data were obtained using a Jeol JMS-SX 102A mass spectrometer at the Analytical Services of the Universidad de Sevilla (CITIUS). Microanalyses were performed by the Microanalytical Service of the Instituto de Investigaciones Químicas. Infrared spectra were recorded on Bruker Vector 22 spectrometer. The NMR instruments were Bruker DRX-500, DRX-400, AdvanceIII-400/R and DRX-300 spectrometers. Spectra were referenced to external SiMe4 (δ: 0 ppm) using the residual proton solvent peaks as internal standards (1H NMR experiments), or the characteristic resonances of the solvent nuclei (13C NMR experiments), while 31P was referenced to external H3PO4. Spectral assignments were made by routine one- and twodimensional NMR experiments (1H, 13C, 13C{1H}, 31P{1H}, COSY, NOESY, HSQC and HMBC) where appropriate. [Au(THT)Cl] (THT = Chapter I. Organometallic Compounds of Gold(I) Stabilized by Coordination to a Terphenylphosphine Ligand 90 tetrahydrothiophene)53a and NaBArF (BArF = B[3,5-(CF3)2C6H3)]4)53b were prepared according to the literature. The 1H and 13C{1H} NMR spectral data for the BArF- anion in CD2Cl2 are identical for all complexes and therefore are not repeated below. BArF-: 1H RMN: δ 7.75 (s, 8H, o-Ar), 7.58 (s, 4H, p-Ar). 13C{1H} RMN: δ 162.1 (q, 4JCF = 37 Hz, ipso-Ar), 135.3 (o-Ar), 129.2 (q, 2JCF = 31 Hz, m-Ar), 124.9 (q, 1JCF = 273 Hz, CF3), 117.8 (p-Ar). All aromatic couplings are of ca. 7.5 Hz. 53 a) R. Uson, A. Laguna, M. Laguna, D. A. Briggs, H. H. Murray, J. P. Fackler., Inorg. Synth. 2007, 26, 85–91; b) N. A. Yakelis, R. G. Bergman, Organometallics 2005, 24, 3579-3581. Chapter I. Organometallic Compounds of Gold(I) Stabilized by Coordination to a Terphenylphosphine Ligand 91 III.4.2. Synthesis and characterization of the new complexes obtained. Synthesis of PMe2ArDipp2. This ligand was prepared in ca. 55 % yield using the procedure already described in detail54 for the analogous phosphine PMe2ArXyl2, but utilizing the Grignard reagent Mg(ArDipp2)Br.55 Yield: 8.72 g (54%). Anal. Calc. for C32H43P: C, 83.80; H, 9.45. Found: C, 83.75; H, 9.85. 1H NMR (300 MHz, CDCl3, 25 ºC): δ 0.70 (d, 2JHP = 5.0 Hz, 6H, (CH3)2-P), 1.05 (d, 3JHH = 6.8 Hz, 12H, CH3-Dipp), 1.25 (d, 3JHH = 6.8 Hz, 12H, CH3-Dipp), 2.66 (h, 3JHH = 6.8 Hz, 4H, CH-Dipp), 7.05 (dd, 3JHH = 7.6 Hz, 4JHP = 2.0 Hz, 2H, m-C6H3), 7.19 (d, 3JHH = 7.7 Hz, 4H, m-Dipp), 7.30 (t, 3JHH = 7.6 Hz, 1H, p-C6H3), 7.36 (t, 3JHH = 7.7 Hz, 2H, p-Dipp) ppm. 13C{1H} NMR (100 MHz, CD2Cl2, 25 ºC): δ 13.7 (d, 1JCP = 14 Hz, (CH3)2-P), 22.6 (s, CH3-Dipp), 25.7 (s, CH3-Dipp), 31.2 (s, CH-Dipp), 122.8 (s, m-Dipp), 127.0 (s, p-C6H3), 128.3 (s, p-Dipp), 131.2 (d, 3JCP = 2 Hz, m-C6H3), 138.4 (d, 1JCP = 28 Hz, ipso-C6H3), 140.4 (d, 3JCP = 4 Hz, ipso-Dipp), 145.2 (d, 2JCP = 15 Hz, o-C6H3), 147.1 (s, o-Dipp) ppm. 31P{1H} NMR (160 MHz, CD2Cl2, 25 ºC): δ -41.3 (s) ppm. 54 J. Campos, L. Ortega-Moreno, S. Conejero, R. Peloso, J. López-Serrano, C. Maya, E. Carmona, Chem. Eur. J. 2015, 21, 8883-8896. 55 a) P. P. Power, Main Group Chemistry 1998, 2, 275-283; b) E. Rivard, P. P. Power, Inorg. Chem. 2007, 46, 10047-10064. Chapter I. Organometallic Compounds of Gold(I) Stabilized by Coordination to a Terphenylphosphine Ligand 92 Synthesis of complex 1. A solution of the phosphine PMe2Ar (Ar = C6H3-o-(C6H3-o- iPr2)2) (430 mg, 0.94 mmol) in toluene (10 mL) was added over a suspension of [Au(THT)Cl] (THT = tetrahydrotiophene) (300 mg, 0.94 mmol) in toluene (5 mL). The initial white suspension became a solution after several hours and was stirred for an overall period of 8 hours. The solvent was then removed under vacuum and the resulting white solid washed with pentane and dried to give compound 1, as a fine white powder, in ca. 90% yield. They can be recrystallized by slow diffusion, at -20 ºC, of pentane into a CH2Cl2 solution (2:1 by vol.). Anal. Calc. for C32H43AuClP: C, 55.6; H, 6.3. Found: C, 55.6; H, 6.1. 1H NMR (500 MHz, 25 ºC, CD2Cl2) δ: 7.55 (td, 1 H, 5JHP = 1.9 Hz, Hd), 7.48 (t, 2 H, 2 Hb), 7.27 (d, 4 H, 4 Ha), 7.24 (dd, 2 H, 4JHP = 4.0 Hz, 2 Hc), P4 3 3 2 2 1 1 1 1 iPr iPr iPr iPr Au Cl HaHb Ha Hc Hd Hc Ha Hb Ha Chapter I. Organometallic Compounds of Gold(I) Stabilized by Coordination to a Terphenylphosphine Ligand 93 2.55 (hept, 4 H, 3JHH = 6.8 Hz, 4 CH(CH3)2), 1.35, 1.05 (d, 12 H each, 3JHH = 6.8 Hz, 4 CH(CH3)2), 1.32 (d, 6 H, 2JHP = 10.0 Hz, PMe2). 13C{1H} NMR (125 MHz, 25 ºC, CD2Cl2) δ: 146.5 (C1), 145.3 (d, 2JCP = 11 Hz, C3), 138.6 (d, 3JCP = 6 Hz, C2), 132.8 (d, 3JCP = 8 Hz, CHa), 129.7 (CHb), 129.2 (CHd), 127.6 (d, 1JCP = 58 Hz, C4), 123.4 (CHc), 31.2 (CH(CH3)2), 25.3, 22.6 (CH(CH3)2), 17.6 (d, 1JCP = 39 Hz, PMe2). 31P{1H} NMR (200 MHz, 25 ºC, CD2Cl2) δ: -5.7. Chapter I. Organometallic Compounds of Gold(I) Stabilized by Coordination to a Terphenylphosphine Ligand 94 Synthesis of complex 2. To a suspension of complex 1 (140 mg, 0.20 mmol) in toluene (10 mL) was added one equivalent of AgNTf2 (80 mg, 0.20 mmol) and the mixture stirred at room temperature for 1 hour. After filtering the resulting suspension the volatiles were removed in vacuo to yield complex 2, as white a powder, in ca. 80% yield. It can be recrystallized by slow diffusion at -20 ºC of pentane into a CH2Cl2 solution (2:1 by vol.). Anal. Calc. for C34H48AuP: C, 43.6; H, 4.6; N, 1.5; S, 6.8. Found: C, ; H, ; N; S. 1H NMR (300 MHz, 25 ºC, CD2Cl2) δ: 7.63 (td, 1 H, 3JHH = 7.6, 5JHP = 1.9 Hz, Hd), 7.49 (t, 2 H, 3JHH = 7.8 Hz, 2 Hb), 7.34 (d, 4 H, 3JHH = 8.1 Hz, 4 Ha), 7.30 (dd, 2 H, 3JHH = 7.7, 4JHP = 3.8 Hz, 2 Hc), 2.51 (hept, 4 H, 3JHH = P 4 3 3 2 2 1 1 1 1 iPr iPr iPr iPr Au N Ha Hb Ha Hc Hd Hc Ha Hb Ha S S F3CO O CF3 O O Chapter I. Organometallic Compounds of Gold(I) Stabilized by Coordination to a Terphenylphosphine Ligand 95 6.8 Hz, 4 CH(CH3)2), 1.44 (d, 6 H, 2JHP = 11.0 Hz, PMe2), 1.35, 1.08 (d, 12 H each, 3JHH = 6.9 Hz, CH(CH3)2). 13C{1H} NMR (75 MHz, 25 ºC, CD2Cl2) δ: 146.7 (C1), 145.9 (d, 2JCP = 11 Hz, C3), 138.1 (d, 3JCP = 6 Hz, C2), 133.2 (d, 3JCP = 8 Hz, CHc), 130.7 (d, 4JCP = 3 Hz, CHd), 129.6 (CHb), 124.9 (d, 1JCP = 65 Hz, C4), 124.2 (CHa), 119.7 (q, 1JCF = 323 Hz, CF3), 31.6 (CH(CH3)2), 25.5, 22.6 (CH(CH3)2), 17.8 (d, 1JCP = 40 Hz, PMe2). 31P{1H} NMR (120 MHz, 25 ºC, CD2Cl2) δ: -11.5. Chapter I. Organometallic Compounds of Gold(I) Stabilized by Coordination to a Terphenylphosphine Ligand 96 Synthesis of complex 3. To a suspension of complex 1 (140 mg, 0.20 mmol) in toluene (10 mL) was added one equivalent of AgMs (40 mg, 0.20 mmol) and the mixture stirred at room temperature for 1 hour. The resulting suspension was then filtered and the volatiles were removed in vacuo to give complex 3, as a white powder, in ca. 80% yield. It can be recrystallized by slow diffusion, at -20 ºC, of pentane into a CH2Cl2 solution (2:1 by vol.). Anal. Calc. for C33H46AuPO3S: C, 52.8; H, 6.2; S, 4.3. Found: C, ; H, ; S. 1H NMR (400 MHz, 25 ºC, CD2Cl2) δ: 7.61 (t, 1 H, 3JHH = 7.7 Hz, Hd), 7.52 (t, 2 H, 3JHH = 7.8 Hz, 2 Hb), 7.34 (d, 4 H, 3JHH = 7.9 Hz, 4 Ha), 7.30 (dd, 2 H, 3JHH = 7.7, 4JHP = 3.8 Hz, 2 Hc), 2.70 (s, 3 H, Me), 2.56 (hept, 4 H, 3JHH = 7.0 Hz, 4 CH(CH3)2), 1.43 (d, 6 H, 2JHP = 11.1 Hz, PMe2), 1.39, 1.09 (d, 12 H each, 3JHH = 6.8 Hz, 4 CH(CH3)2). P4 3 3 2 2 1 1 1 1 iPr iPr iPr iPr Au O HaHb Ha Hc Hd Hc Ha Hb Ha S O Me O Chapter I. Organometallic Compounds of Gold(I) Stabilized by Coordination to a Terphenylphosphine Ligand 103 2.63 (hept, 4 H, 3JHH = 6.8 Hz, 4 CH(CH3)2), 1.38, 1.07 (d, 12 H each, 3JHH = 6.8 Hz, 4 CH(CH3)2), 1.17 (d, 6 H, 2JHP = 7.4 Hz, PMe2), -0.35 (d, 3 H, 3JHP = 8.3 Hz, AuMe). 13C{1H} NMR (100 MHz, 25 ºC, CD2Cl2) δ: 146.5 (C1), 145.7 (d, 2JCP = 11 Hz, C3), 139.6 (d, 4JCP = 5 Hz, C2), 132.5 (d, 3JCP = 7 Hz, CHa), 128.7 (d, 4JCP = 2 Hz, CHb), 128.4 (CHd), 127.6 (d, 1JCP = 58 Hz, C4), 123.0 (CHc), 31.1 (CH(CH3)2), 25.3, 22.5 (CH(CH3)2), 16.4 (d, 1JCP = 30 Hz, PMe2), 5.0 (d, 2JCP = 102 Hz, AuMe). 31P{1H} NMR (160 MHz, 25 ºC, CD2Cl2) δ: 18.9. Chapter I. Organometallic Compounds of Gold(I) Stabilized by Coordination to a Terphenylphosphine Ligand 104 Complex 6b: Anal. Calc. for C34H48AuP: C, 59.6; H, 7.1. Found: C, 59.5; H, 7.0. 1H NMR (500 MHz, 25 ºC, CD2Cl2) δ: 7.46 (td, 1 H, 3JHH = 7.6, 5JHP = 1.7 Hz, Hd), 7.41 (t, 2 H, 3JHH = 7.8 Hz, 2 Hb), 7.25 (d, 4 H, 3JHH =7.8 Hz, 4 Ha), 7.17 (dd, 2 H, 3JHH = 7.5, 4JHP = 2.8 Hz, 2 Hc), 2.60 (hept, 4 H, 3JHH = 6.8 Hz, 4 CH(CH3)2), 1.36, 1.04 (d, 12 H each, 3JHH = 6.8 Hz, 4 CH(CH3)2), 1.11 (d, 6 H, 2JHP = 7.2 Hz, PMe2), 1.00 (td, 3 H, 3JHH = 8.7, 4JHP = 8.2 Hz, AuCH2CH3), 0.48 (qd, 2 H, 3JHH = 8.7, 3JHP = 8.1 Hz, AuCH2CH3). 13C{1H} NMR (125 MHz, 25 ºC, CD2Cl2) δ: 146.9 (C1), 146.0 (d, 2JCP = 11 Hz, C3), 139.9 (d, 3JCP = 5 Hz, C2), 133.1 (d, 1JCP = 31 Hz, C4), 132.8 (d, 3JCP = 7 Hz, CHc), 129.0 (CHd), 128.8 (CHb), 123.3 (CHa), 31.5 (CH(CH3)2), 25.6, 28.9 (CH(CH3)2), 19.8 (d, 2JCP = 104; 1JCH = 134 Hz, AuCH2CH3), 16.7 (d, 3JCP = 5 Hz, AuCH2CH3), 16.7 (d, 1JCP = 29 Hz, PMe2). 31P{1H} NMR (200 MHz, 25 ºC, CD2Cl2) δ: 19.5. P4 3 3 2 2 1 1 1 1 iPr iPr iPr iPr Au CH2CH3 HaHb Ha Hc Hd Hc Ha Hb Ha Chapter I. Organometallic Compounds of Gold(I) Stabilized by Coordination to a Terphenylphosphine Ligand 105 Complex 6c: Anal. Calc. for C34H48AuP: C, 63.9; H, 7.2. Found: C,; H,. 1H NMR (400 MHz, 25 ºC, CD2Cl2) δ: 7.47 (td, 1 H, 3JHH = 7.5, 5JHP = 1.6 Hz, Hd), 7.44 (t, 2 H, 3JHH = 7.8 Hz, 2 Hb), 7.42 (dd, 2 H, 3JHH = 8.4, 4JHH = 1.2 Hz, 2 Ho), 7.26 (d, 4 H, 3JHH = 7.8 Hz, 4 Ha), 7.18 (dd, 2 H, 3JHH = 7.6, 4JHP = 2.8 Hz, 2 Hc), 7.17 (t, 2 H, 3JHH = 7.7 Hz, 2 Hm), 7.02 (tt, 1 H, 3JHH = 7.3, 4JHH = 1.3 Hz, Hp), 2.59 (hept, 4 H, 3JHH = 6.8 Hz, 4 CH(CH3)2), 1.36, 105 (d, 12 H each, 3JHH = 6.8 Hz, CH(CH3)2), 1.23 (s, 6 H, CMe2), 1.10 (d, 6 H, 2JHP = 7.2 Hz, PMe2), 0.94 (d, 2 H, 3JHP = 8.4 Hz, AuCH2). 13C NMR (100 MHz, 25 ºC, CD2Cl2) δ: 156.9 (d, 4JCP = 6 Hz, CqPh), 146.5 (C1), 145.8 (d, 2JCP = 11 Hz, C3), 139.5 (d, 3JCP = 4 Hz, C2), 132.6 (d, 1JCP = 32 Hz, C4), 132.4 (d, 3JCP = 6 Hz, CHc), 128.7 (d, 4JCP = 2 Hz, CHd), 128.4 (CHm), 127.2 (CHb), 125.6 (CHo), 123.9 (CHp), 123.0 (CHa), 50.8 (d, 2JCP = 101; 1JCH = 119 Hz, AuCH2), 40.9 (d, 3JCP = 3 Hz, CMe2), 35.2 (d, 4JCP = 4 Hz, CMe2), 31.1 (CH(CH3)2), 25.3, 22.5 (CH(CH3)2), 16.2 (d, 1JCP = 29 Hz, PMe2). 31P NMR (160 MHz, 25 ºC, CD2Cl2) δ: 18.8. P4 3 3 2 2 1 1 1 1 iPr iPr iPr iPr Au CH2 HaHb Ha Hc Hd Hc Ha Hb Ha Me Me Chapter I. Organometallic Compounds of Gold(I) Stabilized by Coordination to a Terphenylphosphine Ligand 106 Complex 6d: Anal. Calc. for C38H48AuP: C, 62.3; H, 6.6. Found: C, 62.1; H, 6.8. 1H NMR (500 MHz, 25 ºC, CD2Cl2) δ: 7.52 (t, 1 H, 3JHH = 7.7, Hd), 7.36 (t, 2 H, 3JHH = 7.6 Hz, 2 Hb), 7.28 (d, 4 H, 3JHH =7.8 Hz, 4 Ha), 7.22 (dd, 2 H, 3JHH = 7.6, 4JHP = 2.8 Hz, 2 Hc), 7.06, 6.91 (m, 5 H, HPh), 2.65 (hept, 4 H, 3JHH = 6.8 Hz, 4 CH(CH3)2), 1.42, 1.08 (d, 12 H, 3JHH = 6.8 Hz, 4 CH(CH3)2), 1.26 (d, 6 H, 2JHP = 7.7 Hz, PMe2). 13C{1H} NMR (125 MHz, 25 ºC, CD2Cl2) δ: 171.2 (d, 2JCP = 123 Hz, AuCq(Ph)), 146.9 (C1), 146.1 (d, 2JCP = 11 Hz, C3), 139.8 (CHm(Ph)), 139.5 (d, 3JCP = 5 Hz, C2), 132.8 (d, 3JCP = 7 Hz, CHc), 131.6 (d, 1JCP = 38 Hz, C4), 129.3 (d, 4JCP = 2 Hz, CHd), 129.1 (CHb), 126.9 (d, 3JCP = 6 Hz, CHo(Ph)), 124.6 (CHp(Ph)), 123.5 (CHa), 31.5 (CH(CH3)2), 25.6, 23.0 (CH(CH3)2), 16.9 (d, 1JCP = 31 Hz, PMe2). 31P{1H} NMR (200 MHz, 25 ºC, CD2Cl2) δ: 13.8. P4 3 3 2 2 1 1 1 1 iPr iPr iPr iPr Au HaHb Ha Hc Hd Hc Ha Hb Ha Chapter I. Organometallic Compounds of Gold(I) Stabilized by Coordination to a Terphenylphosphine Ligand 107 Complex 6e: Anal. Calc. for C34H46AuP: C, 59.8; H, 6.8. Found: C, ; H, . 1H NMR (400 MHz, 25 ºC, CD2Cl2) δ: 7.52 (t, 1 H, 3JHH = 7.7, Hd), 7.45 (t, 2 H, 3JHH = 7.8 Hz, 2 Hb), 7.30 (d, 4 H, 3JHH = 7.8 Hz, 4 Ha), 7.23 (dd, 2 H, 3JHH = 7.6, 4JHP = 2.9 Hz, 2 Hc), 6.37 (ddd, 1 H, 3JHH = 20.2, 3JHH = 13.8, 3JHP = 6.0 Hz, AuCHe=CH2), 5.57 (ddd, 1 H, 3JHH = 13.8, 2JHH = 5.4, 4JHP = 19.3 Hz, AuCHe=CHgHf), 4.96 (ddd, 1 H, 3JHH = 20.6, 2JHH = 5.3, 4JHP = 8.9 Hz, AuCHe=CHgHf), 2.62 (hept, 4 H, 3JHH = 6.8 Hz, 4 CH(CH3)2), 1.40, 1.08 (d, 12 H each, 3JHH = 6.8 Hz, 4 CH(CH3)2), 1.20 (d, 6 H, 2JHP = 7.7 Hz, PMe2). 13C{1H} NMR (100 MHz, 25 ºC, CD2Cl2) δ: 168.4 (d, 2JCP = 125; 1JCH = 136 Hz, AuCH=CH2), 146.5 (C1), 145.6 (d, 2JCP = 11 Hz, C3), 139.2 (d, 3JCP = 5 Hz, C2), 132.5 (d, 3JCP = 7 Hz, CHc), 131.5 (d, 1JCP = 38 Hz, C4), 128.9 (d, 5JCP = 2 Hz, CHd), 128.6 (CHb), 128.4 (1JCH = 154, 149 Hz, AuCH=CH2), 123.1 (CHa), 31.2 (CH(CH3)2), 25.3, 22.6 (CH(CH3)2), 16.4 (d, 1JCP = 31 Hz, PMe2). 31P{1H} NMR (160 MHz, 25 ºC, CD2Cl2) δ: 14.9. P4 3 3 2 2 1 1 1 1 iPr iPr iPr iPr Au C HaHb Ha Hc Hd Hc Ha Hb Ha C He HgHf Chapter I. Organometallic Compounds of Gold(I) Stabilized by Coordination to a Terphenylphosphine Ligand 108 Complex 6f: Anal. Calc. for C34H44AuP: C, 60.0; H, 6.5. Found: C, 60.0; H, 6.1. 1H NMR (400 MHz, 25 ºC, CD2Cl2) δ: 7.55 (t, 1 H, 3JHH = 7.7, Hd), 7.48 (t, 2 H, 3JHH = 7.8 Hz, 2 Hb), 7.32 (d, 4 H, 3JHH = 7.8 Hz, 4 Ha), 7.25 (dd, 2 H, 3JHH = 7.5, 4JHP = 3.3 Hz, 2 Hc), 2.59 (hept, 4 H, 3JHH = 6.9 Hz, 4 CH(CH3)2), 1.40, 1.08 (d, 12 H each, 3JHH = 6.7 Hz, 4 CH(CH3)2), 1.36 (d, 1 H, 4JHP = 6.1 Hz, AuC≡CH), 1.24 (d, 6 H, 2JHP = 8.7 Hz, PMe2). 13C{1H} NMR (100 MHz, 25 ºC, CD2Cl2) δ: 146.5 (C1), 145.5 (d, 2JCP = 11 Hz, C3), 138.7 (d, 3JCP = 5 Hz, C2), 132.6 (d, 3JCP = 7 Hz, CHc), 129.3 (CHd), 129.1 (d, 1JCP = 50 Hz, C4), 129.0 (CHb), 126.0 (d, 2JCP = 147; 2JCH = 40 Hz, AuC≡CH), 123.4 (CHa), 87.8 (d, 3JCP = 28; 1JCH = 226 Hz, AuC≡CH), 31.2 (CH(CH3)2), 25.3, 22.6 (CH(CH3)2), 16.6 (d, 1JCP = 34 Hz, PMe2). 31P{1H} NMR (160 MHz, 25 ºC, CD2Cl2) δ: 7.1. P4 3 3 2 2 1 1 1 1 iPr iPr iPr iPr Au HaHb Ha Hc Hd Hc Ha Hb Ha H Chapter I. Organometallic Compounds of Gold(I) Stabilized by Coordination to a Terphenylphosphine Ligand 109 Synthesis of complex 1·Br. To a suspension of complex 1 (140 mg, 0.20 mmol) in toluene (10 mL) was added 1.2 equiv. of a commercial solution of Mg(C≡CH)Br at -40 ºC, and the mixture was then stirred at room temperature for 3 hours. Evaporation of the volatiles led to compound 7 as white powder in ca. xx% yield. It can be recrystallized by slow diffusion, at -20 ºC, of pentane into a CH2Cl2 solution (2:1 by vol.). Anal. Calc. for C32H43AuBrP: C, 52.2; H, 5.5. Found: C,; H,. 1H NMR (400 MHz, 25 ºC, CD2Cl2) δ: 7.55 (t, 1 H, 3JHH = 7.7 Hz, Hd), 7.49 (t, 2 H, 3JHH = 7.7 Hz, 2 Hb), 7.27 (d, 4 H, 3JHH =7.9 Hz, 4 Ha), 7.25 (dd, 2 H, 3JHH = 7.7, 4JHP = 3.3 Hz, 2 Hc), 2.57 (hept, 4 H, 3JHH = 6.7 Hz, 4 CH(CH3)2), 1.36, 1.05 (d, 12 H each, 3JHH = 6.8 Hz, 4 CH(CH3)2), 1.32 (d, 6 H, 2JHP = 10.3 Hz, PMe2). P4 3 3 2 2 1 1 1 1 iPr iPr iPr iPr Au Br HaHb Ha Hc Hd Hc Ha Hb Ha Chapter I. Organometallic Compounds of Gold(I) Stabilized by Coordination to a Terphenylphosphine Ligand 110 13C{1H} NMR (100 MHz, 25 ºC, CD2Cl2) δ: 147.3 (C1), 146.2 (d, 2JCP = 11 Hz, C3), 139.4 (d, 3JCP = 5 Hz, C2), 133.7 (d, 3JCP = 8 Hz, CHc), 130.5 (d, 4JCP = 2 Hz, CHd), 130.1 (CHb), 129.0 (d, 1JCP = 56 Hz, C4), 124.3 (CHa), 32.1 (CH(CH3)2), 26.1, 23.5 (CH(CH3)2), 18.4 (d, 1JCP = 38 Hz, PMe2). 31P{1H} NMR (160 MHz, 25 ºC, CD2Cl2) δ: -1.18. Chapter I. Organometallic Compounds of Gold(I) Stabilized by Coordination to a Terphenylphosphine Ligand 111 Synthesis of complexes 7a-7c, 9, 10 and 11. An equimolar mixture of the corresponding hydrocarbyl compound (0.07 mmol) and complex 2 (70 mg, 0.07 mmol) was dissolved in CH2Cl2 (5 mL) and stirred for 10 minutes. The solution was then evaporated to dryness to afford compounds 7a-7c, 9, 10 and 11 in ca. 90% yield. They can be recrystallized by slow diffusion, at -20 ºC, of pentane into a CH2Cl2 solution (2:1 by vol.). Complex 7a: Anal. Calc. for C89H89Au2BF20P2: C, 53.31; H, 4.47. Found: C, 53.0; H, 4.5. 1H NMR (400 MHz, 25 ºC, CD2Cl2) δ: 7.60 (t, 2 H, 2 Hd), 7.49 (t, 4 H, 4 Hb), 7.24 (d, 12 H, 8 Ha, 4 Hc), 2.46 (hept, 8 H, 3JHH = 6.9 Hz, 8 Au Au + H3 C NTf2 - P 4 3 3P 4 3 3 21 1 iPr iPr 2 11 iPr iPr 12 1 iPr iPr 1 2 1 iPr iPr Hc Hd HcHc Hd Hc Ha Hb Ha Ha Hb Ha HaHb Ha Hb Ha Ha Chapter I. Organometallic Compounds of Gold(I) Stabilized by Coordination to a Terphenylphosphine Ligand 112 CH(CH3)2), 1.26, 1.05 (d, 24 H each, 3JHH = 6.7 Hz, 8 CH(CH3)2), 1.25 (d, 12 H, 2JHP = 9.1 Hz, 2 PMe2), 0.34 (s, 3 H, Au2Me). 13C{1H} NMR (100 MHz, 25 ºC, CD2Cl2) δ: 146.8 (C1), 145.7 (d, 2JCP = 12 Hz, C3), 138.6 (d, 4JCP = 6 Hz, C2), 133.0 (d, 3JCP = 8 Hz, CHc), 130.6 (CHd), 129.2 (CHb), 128.1 (d, 1JCP = 54 Hz, C4), 123.3 (CHa), 31.2 (CH(CH3)2), 24.9, 22.6 (CH(CH3)2), 16.8 (d, 1JCP = 37 Hz, PMe2), -0.1 (t, 2JCP = 53 Hz; 1JCH = 129 Hz, Au2Me). 31P{1H} NMR (160 MHz, 25 ºC, CD2Cl2) δ: -0.2. Chapter I. Organometallic Compounds of Gold(I) Stabilized by Coordination to a Terphenylphosphine Ligand 119 127.7 (d, 1JCP = 40 Hz, C1), 123.7 (CHc), 31.5 (CH(CH3)2), 24.8, 22.6 (CH(CH3)2), 15.9 (vt, 1JCP = 17 Hz, PMe2). 31P{1H} NMR (200 MHz, CD2Cl2, 25 ºC) δ: 6.3. Chapter I. Organometallic Compounds of Gold(I) Stabilized by Coordination to a Terphenylphosphine Ligand 120 I.5. BIBLIOGRAPHY [1] a) C. Elschenbroich, Organometallics, 3rd Edition, WILEY -VCH Verlag GmbH & Co. KGaA, Weinheim, Germany, 2006; b) M. Bochmann, Organometallics and Catalysis. An Introduction., Oxford University Press, Oxford, UK, 2014; c) J. F. Hartwig, Organotransition Metal Chemistry: From Bonding to Catalysis, University Science Books, Sausalito, 2009; d) R. H. Crabtree, The Organometallic Chemistry of the Transition Metals, Wiley, Hoboken, NJ, 2009. [2] For reviews on this topic, see: a) T. Lauterbach, A. M. Asiri, A. S. K. Hashmi, Adv. Organomet. Chem. 2014, 62, 261-297; b) C. Obradors, A. M. Echavarren, Chem. 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[17] This phospine was prepared and characterized independently to the present work and accordingly it will be reported somewhere else. [18] This work is based on preliminary but seminal studies carried out in this laboratory by Dr. Jesús Campos. [19] These results were first obtained by Dr. Jesús Campos. [20] As already indicated the “half-arrow“ notation (⇀) that appears in structurebonding representations like C in Scheme 1 indicates the existence of a 3c-2e interaction and it is useful for electron-counting purposes. See: J. C. Green, M. L. Green, G. Parkin, Chem. Commun. 2012, 48, 11481-11503. [21] For structurally characterized substituted vinyls of this type see: a) C. M. Wyss, B. K. Tate, J. Bacsa, M. Wieliczko, J. P. Sadighi, Polyhedron 2014, 84, 87-95; b) A. Gomez-Suárez, S. Dupuy, A. M. Z. Slawin, S. P. Nolan, Angew. Chem. Int. Ed. 2013, 52, 938-942; c) A. S. Hashmi, I. Braun, P. Nosel, J. Schadlich, M. Wieteck, M. Rudolph, F. Rominger, Angew. Chem. Int. 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Herein, we will describe new, recent advances in two different areas of research. In the first, the insertion of selected alkynes into the [(C5Me5)Ir(III)]—C σ bond of a cationic species containing a cyclometalated xylyl phosphine will be described, while in the second we will explore the reactivity of a cationic cyclometallated alkylidene containing the anionic ligand TpMe2 (TpMe2 = hydrotris(3,5- dimethylpyrazolyl)borate). In some aspects of its coordination chemistry TpMe2 resembles the C5Me5 anion. Chapter II. Organometallic Complexes of Iridium(III) with Ancillary Pentamethylcyclopentadienyl and Hydrotris(pyrazolyl)borate Ligands 135 Figure 3. Reactivity of complex 2·CH2Cl2 obtained from the chloride 1 by halide abstraction with NaBArF in CH2Cl2, as a function of temperature and the absence or presence of Lewis bases (L) according to reference 6b. Intermediates A and B were proposed to participate in the fast exchange of the metallated and nonmetallated xylyl groups. In all the cases the complementary anion is BArF- = B[3,5-C6H3(CF3)2]4-. The chemistry of complexes 2·CH2Cl2 and 3, obtained (Figure 3) from the neutral chloride [(ƞ5-C5Me5)Ir(C^P)Cl] (1) and NaBArF (BArF- = [B(3,5-C6H3(CF3)2)4]-),14a,14b constitute the starting point for the first part of this Chapter. At room temperature, complex 3 exhibits a solution dynamic behaviour that exchanges the metallated and non-metallated xylyl CH2 P Ir H3CCH2 P Ir H2C H A Ir P Xyl Cl Me CH2Cl2 - 60 ˚C NaBArF Ir P Xyl ClCH2Cl + Me CH2 P Ir H3C L, CH2Cl2 -60 ˚C Ir P Xyl L Me L = NCMe, C5H5N, NH3, CO, PMe3 1 2·CH2Cl2 2·L 3 L, CH2Cl2 25 ˚C -40 ˚C B + + + + Chapter II. Organometallic Complexes of Iridium(III) with Ancillary Pentamethylcyclopentadienyl and Hydrotris(pyrazolyl)borate Ligands 136 termini thanks to a facile variation in the coordination of the metallated benzylic ring, from κ4-P,C,C’,C’’ to κ2-P,C, as revealed by NMR studies.14b This behaviour appears to be exclusive of cyclometallated complexes of this type that contain two xylyl (or xylyl-derived) phosphine substituents. Experimental and computational studies14f revealed that: (i) the putative low energy κ2-P,C intermediate A (Figure 3), featured a very weak agostic interaction; (ii) the probable implication in the exchange of an also low-energy doubly-metallated Ir(V) hydride intermediate B, that resulted from oxidative addition of the agostic C—H bond to Ir(III). In accordance with these arguments, complex 3 reacted readily with a variety of Lewis bases to form the corresponding adducts 2·L, shown in Figure 3 too. As an extension of this work we envisaged studying the reactivity of complex 2·CH2Cl2 toward some selected terminal and internal alkynes.14a,14b,14e Transition metal-alkyne chemistry is an essential part of organometallic chemistry and constitutes an active and exciting area of research.15,16 A common outcome of transition metal-alkyne reactivity is in fact the formation of new C—C bonds, in itself a fundamental reaction in organic synthesis that may occur by alkyne insertion into a M—C bond or by other C—C coupling steps, comprising, for instance the participation of !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! 15 See for instance: a) I. T. Trotus, T. Zimmermann, F. Schuth, Chem. Rev. 2014, 114, 1761-1782; b) J. M. Lynam, Chem. Eur. J. 2010, 16, 8238-8247; c) C. Anaya de Parrodi, P. J. Walsh, Angew. Chem. Int. Ed. 2009, 48, 4679-4682; d) C. Bruneau, P. H. Dixneuf, Angew. Chem. Int. Ed. 2006, 45, 2176-2203; e) F. De Angelis, S. Fantacci, A. Sgamellotti, Coord. Chem. 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Organometallic Complexes of Iridium(III) with Ancillary Pentamethylcyclopentadienyl and Hydrotris(pyrazolyl)borate Ligands 137 vinylidine structures, M=C=C(H)R, resulting from alkyne isomerisation.15,16,17,18 Numerous studies in this field have been based on cyclometallated complexes [(ƞ5-C5Me5)M(C^X)]+ of Rh and Ir and in somewhat related complexes.19,20,21 At variance with the reactivity of alkynes toward Group 10 M—C bonds, that often results in products of multiple insertion, 22 cyclometallated (ƞ5-C5Me5)Rh(III) and (ƞ5- C5Me5)Ir(III) cationic complexes frequently incorporate only one molecule of the alkyne, although in some cases double insertion products have been obtained too.19a,21c !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! 17 a) M. Jimenez-Tenorio, M. C. Puerta, P. Valerga, M. A. Ortuno, G. Ujaque, A. Lledos, Inorg. Chem. 2013, 52, 8919-8932; b) M. Jiménez-Tenorio, M. C. Puerta, P. Valerga, Eur. J. Inorg. Chem. 2004, 2004, 17-32; c) E. Bustelo, J. J. Carbó, A. Lledós, K. Mereiter, M. C. Puerta, P. Valerga, J. Am. Chem. Soc. 2003, 125, 3311-3321; d) I. de los Ríos, M. J. Tenorio, M. C. Puerta, P. Valerga, J. Am. Chem. Soc. 1997, 119, 6529-6538. 18 a) A. J. Arita, J. Cantada, D. B. Grotjahn, A. L. Cooksy, Organometallics 2013, 32, 6867-6870; b) D. B. Grotjahn, E. J. Kragulj, C. D. Zeinalipour-Yazdi, V. Miranda-Soto, D. A. Lev, A. L. Cooksy, J. Am. Chem. Soc. 2008, 130, 10860–10861; c) D. B. Grotjahn, V. Miranda-Soto, E. J. Kragulj, D. A. Lev, G. Erdogan, X. Zeng, A. L. Cooksy, J. Am. Chem. Soc. 2008, 130, 20-21; d) D. B. Grotjahn, X. Zeng, A. L. Cooksy, W. S. Kassel, A. G. DiPasquale, L. N. Zakharov, A. L. Rheingold, Organometallics 2007, 26, 3385-3402; e) D. B. Grotjahn, Chem. Eur. J. 2005, 11, 7146-7153. 19 a) L. Li, Y. Jiao, W. W. Brennessel, W. D. Jones, Organometallics 2010, 29, 4593- 4605; b) L. Li, W. W. Brennessel, W. D. Jones, Organometallics 2009, 28, 3492–3500; c) L. Li, W. W. Brennessel, W. D. Jones, J. Am. Chem. Soc. 2008, 130, 12414–12419. 20 Y.-F. Han, H. Li, P. Hu, G.-X. Jin, Organometallics 2011, 30, 905-911. 21 a) Y. Boutadla, D. L. Davies, O. Al-Duaij, J. Fawcett, R. C. Jones, K. Singh, Dalton Trans. 2010, 39, 10447–10457; b) D. L. Davies, O. Al-Duaij, J. Fawcett, K. Singh, Organometallics 2010, 29, 1413-1420; c) D. L. Davies, S. M. A. Donald, O. Al-Duaij, S. A. Macgregor, M. Pölleth, J. Am. Chem. Soc. 2006, 128, 4210-4211. 22 a) R. Frutos-Pedreño, P. González-Herrero, J. Vicente, P. G. Jones, Organometallics 2012, 31, 3361-3372; b) J. Vicente, I. Saura-Llamas, J. Turpín, D. Bautista, C. Ramírez de Arellano, P. G. Jones, Organometallics 2009, 28, 4175-4195; c) K. R. Reddy, K. Surekha, G.-H. Lee, S.-M. Peng, S.-T. Liu, Organometallics 2001, 20, 5557-5563. Chapter II. Organometallic Complexes of Iridium(III) with Ancillary Pentamethylcyclopentadienyl and Hydrotris(pyrazolyl)borate Ligands 138 II.2.2. Cationic Ir(III) Alkylidenes. Metal alkyls16,23 are at the heart of organometallic chemistry, as their reactive M—C σ bonds participate in many useful reactions. In turn, the chemistry of metal alkylidenes and Fischer carbenes has become one the most successful areas of research in synthesis and catalysis mediated by organometallics, due to the rich reactivity of the M=C bond.24,25,26 Cationic carbene complexes of Ir(III), of type [LnIr=C(R)(R’)]+, in which the carbene ligand is devoid of heteroatom substituents (R and R’ are hydrogen or hydrocarbyl groups) are rare species due to the high reactivity of the greatly electrophilic alkylidene carbon atom.27,28 Iridium compounds of this kind have been studied mainly by our group, since the first example !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! 23 a) P. J. Davidson, M. F. Lappert, R. Pearce, Chem. Rev. 1976, 76, 219-242; b) R. R. Schrock, G. W. Parshall, Chem. Rev. 1976, 76, 243-268; c) G. Wilkinson, Chimia 1973, 27, 165-169. 24 a) R. H. Grubbs, Angew. Chem. Int. Ed. 2006, 45, 3760-3765; b) R. R. Schrock, Angew. Chem. Int. Ed. 2006, 45, 3748-3759; c) Y. Chauvin, Angew. Chem. Int. Ed. 2006, 45, 3741 – 3747 . 25 a) J. W. Herndon, Coord. Chem. Rev. 2011, 255, 3-100; b) A. J. Arduengo, G. Bertrand, Chem. Rev. 2009, 109, 3209–3210. 26 a) K. G. Caulton, J. Organomet. Chem. 2001, 617-618, 56–64; b) F. Z. Do!rwald, Metal Carbenes in Organic Synthesis, Wiley-VCH, Weinheim, Germany, 1999. 27 For recent examples of electrophilic late-transition-metal alkylidenes, see the following citations and those in reference 28: a) M. Joost, L. Estevez, S. Mallet-Ladeira, K. Miqueu, A. Amgoune, D. Bourissou, Angew. Chem. Int. Ed. 2014, 53, 14512-14516; b) Y. Wang, M. E. Muratore, Z. Rong, A. M. Echavarren, Angew. Chem. Int. Ed. 2014, 53, 14022- 14026; c) M. W. Hussong, F. Rominger, P. Kramer, B. F. Straub, Angew. Chem. Int. Ed. 2014, 53, 9372-9375; d) R. J. Harris, R. A. Widenhoefer, Angew. Chem. Int. Ed. 2014, 53, 9369-9371; e) D. H. Ringger, I. J. Kobylianskii, D. Serra, P. Chen, Chem. Eur. J. 2014, 20, 14270-14281; f) J. Campos, R. Peloso, E. Carmona, Angew. Chem. Int. Ed. 2012, 51, 8255-8258. 28 a) A. Fürstner, Angew. Chem. Int. Ed. 2014, 53, 8587-8598; b) A. S. K. Hashmi, Acc. Chem. Res. 2014, 47, 864–876; c) Y.-M. Wang, A. D. Lackner, F. D. Toste, Acc. Chem. Res. 2014, 47, 889–901; d) C. Obradors, A. M. Echavarren, Acc. Chem. Res. 2014, 47, 902–912; e) H.-S. Yeom, S. Shin, Acc. Chem. Res. 2014, 47, 966–977; f) L. Fensterbank, M. Malacria, Acc. Chem. Res. 2014, 47, 953–965; g) A. Fürstner, Acc. Chem. Res. 2014, 47, 925–938; h) D.-H. Zhang, X.-Y. Tang, M. Shi, Acc. Chem. Res. 2014, 47, 913–924. Chapter II. Organometallic Complexes of Iridium(III) with Ancillary Pentamethylcyclopentadienyl and Hydrotris(pyrazolyl)borate Ligands 139 of a cationic Ir(III) alkylidene was published in 1998 by protonation of an alkenyl complex with HBArF (Figure 4), 29 taking advantage of the stabilizing properties provided by the ancillary TpMe2 ligand30 (TpMe2 = hydrotris(3,5-dimethylpyrazolyl)borate). The last examples of this type of species recently reported for our group31 are derivatives of (C5Me5)Ir(III) constructed around cyclometallated phosphines that contain at least one xylyl unit. Figure 4. Generation of the first Ir(III) alkylidene by protonation of a Ir-vinyl complex. The hydrotris(3,5-dimethylpyrazolyl)borate, a ligand used in our group for decades, is considered analogous to the pentamethylcyclopentadienyl ligand, because they have some important characteristics in common, such as their capacity to occupy three positions in the metal coordination sphere, both are six electrons donor (or five !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! 29 F. M. Alías, M. L. Poveda, M. Sellin, E. Carmona, J. Am. Chem. Soc. 1998, 120, 5816- 5817. 30 a) M. Besora, S. F. Vyboishchikov, A. Lledós, F. Maseras, E. Carmona, M. L. Poveda, Organometallics 2010, 29, 2040-2045; b) F. M. Alías, M. L. Poveda, M. Sellin, E. Carmona, Organometallics 1998, 17, 4124-4126; c) Y. Alvarado, P. J. Daff, P. J. Pérez, M. L. Poveda, R. Sánchez-Delgado, E. Carmona, Organometallics 1996, 15, 2192-2194. 31 J. Campos, E. Carmona, Organometallics 2015, 34, 2212–2221. Me3P [Ir] HH+, -60 ºC Me3P [Ir] H H Me + (Carmona, 1998) Chapter II. Organometallic Complexes of Iridium(III) with Ancillary Pentamethylcyclopentadienyl and Hydrotris(pyrazolyl)borate Ligands 140 depending on the formalism utilized) and they are formally monoanionic.32 The TpMe2 ligand has demonstrated a splendid capacity to stabilize transition metal complexes, inducing a peculiar and fruitful reactivity. Nitriles, R-C≡N, are isolectronic with other unsaturated ligands such as dinitrogen, carbon monoxide, isocyanides and alkynes, and form an important family of ligands, with well-recognized coordination and chemical reactivity properties.33,34 This type of ligands are extensively used for the preparation of transition metal complexes from which, owing to their weak σ donor and π acceptor ability, they can be readily displaced to afford novel coordination and organometallic complexes. In this Chapter we will discuss in detail the formation of a surprisingly stable cationic iridium-alkylidene bearing TpMe2 and nitrile as ligands.33 This species allowed for the realization of a clean, waterpromoted, transformation (MeCN-H2O, 100 ºC) into an iridabicyclic !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! 32 S. Trofimenko, Chem. Rev. 1993, 93, 943–980. 33 a) V. Y. Kukushkin, A. J. L. Pombeiro, Chem. Rev. 2002, 102, 1771-1802; b) R. A. Michelin, M. Mozzon, R. Bertani, Coord. Chem. Rev. 1996, 147, 299-338. 34 a) J. Lasri, S. Gupta, M. F. C. G. da Silva, A. J. L. Pombeiro, Inorg. Chem. Commun. 2012, 18, 69-72; b) N. A. Bokach, M. L. Kuznetsov, V. Y. Kukushkin, Coord. Chem. Rev. 2011, 255, 2946-2967; c) J. J. Garcia, P. Zerecero-Silva, G. Reyes-Rios, M. G. Crestani, A. Arevalo, R. Barrios-Francisco, Chem. Commun. 2011, 47, 10121-10123; d) M. G. Crestani, A. Steffen, A. M. Kenwright, A. S. Batsanov, J. A. K. Howard, T. B. Marder, Organometallics 2009, 28, 2904–2914; e) P. V. Gushchin, K. V. Luzyanin, M. N. Kopylovich, M. Haukka, A. J. L. Pombeiro, V. Y. Kukushkin, Inorg. Chem. 2008, 47, 3088-3094; f) T. A. Atesin, T. Li, S. Lachaize, W. W. Brennessel, J. J. García, W. D. Jones, J. Am. Chem. Soc. 2007, 129, 7562-7569; g) J. Vicente, J. A. Abad, M. J. Lopez- Saez, P. G. Jones, Angew. Chem. Int. Ed. 2005, 44, 6001-6004; h) B. d. Bruin, M. J. Boerakker, R. d. Gelder, J. M. M. Smits, A. W. Gal, Angew. Chem. Int. Ed. 1999, 38, 219- 222. Chapter II. Organometallic Complexes of Iridium(III) with Ancillary Pentamethylcyclopentadienyl and Hydrotris(pyrazolyl)borate Ligands 141 complex with an aesthetically attractive structure which resembles that of the organic molecule barrelene,35 HC(CH=CH)3CH (Figure 5). Figure 5. Structures of barrelene (left) and of the iridabicyclic Ir(III) cationic complex resembling the former (right). !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! 35 a) H. E. Zimmerman, G. L. Grunewald, R. M. Paufler, M. A. Sherwin, J. Am. Chem. Soc. 1969, 91, 2330-2338; b) H. E. Zimmerman, R. M. Paufler, J. Am. Chem. Soc. 1960, 82, 1514–1515. [Ir] HN HN + Ir B N N N N N N H [Ir] TpMe2 Ir Chapter II. Organometallic Complexes of Iridium(III) with Ancillary Pentamethylcyclopentadienyl and Hydrotris(pyrazolyl)borate Ligands 142 II.3. RESULTS AND DISCUSSION II.3.1. Reactivity of Complex 1 with Alkynes. II.3.1.1. Reaction of Complex 1 with NaBArF in the Presence of Acetylene. When the reaction of compound 1 with NaBArF was performed under an atmosphere of acetylene (1 bar, CH2Cl2, 25 ºC) the cationic adduct 2·HC≡CH cleanly formed (Scheme 1). After the appropriate workup, this species was isolated, as a pale yellow solid, in ca. 70% yield. Scheme 1. Synthesis of the adduct 2·HC≡CH. CH2Cl2, 25 ˚C Ir P Xyl Cl Me Ir P Xyl + Me H H 12· HC CH NaBArF, HC CH BArF- Chapter II. Organometallic Complexes of Iridium(III) with Ancillary Pentamethylcyclopentadienyl and Hydrotris(pyrazolyl)borate Ligands 143 This complex was completely characterized by the usual techniques, including NMR spectroscopy. Its 500 MHz 1H NMR spectrum (CD2Cl2, 25 ºC, Figure 4) is in accord with the proposed structure and reveals the fast rotation on the NMR time scale, of the acetylene ligand around the Ir— C2H2 bond axis, with the two protons becoming equivalent and appearing as a single doublet (3JHP = 1.8 Hz) at 4.16 ppm. Lowering the temperature to -60 ºC allowed the differentiation of these two 1H nuclei, which now resonate at 4.35 (s) and 4.22 (d, 3JHP = 2.7 Hz) ppm (Figure 1). On the other hand, the IrCH2 protons fortuitously have the same chemical shift at 25 ºC in CD2Cl2, but cooling permits their discrimination, with Δδ becoming larger at lower temperatures, such that at -60 ºC they appear at 4.04 and 3.92 ppm (d, 2JHH = 13.8 Hz) (Figure 4). Chapter II. Organometallic Complexes of Iridium(III) with Ancillary Pentamethylcyclopentadienyl and Hydrotris(pyrazolyl)borate Ligands 144 Figure 4. Dynamic behaviour of 2·HC≡CH as revealed by variable temperature 1H NMR spectroscopy (CD2Cl2, 500 MHz). Single-crystal X-ray studies confirmed the molecular structure of complex 2·HC≡CH. An ORTEP view of the cation is shown in Figure 5. This species exhibit Ir—CH2 and Ir—P bonds to the metallated phosphine of 2.140(5) and 2.2849(14) Å, respectively, which are comparable to those found for other 2·L adducts.14b The Ir—C2H2 linkage is characterized by Ir—C bond distances of 2.152(6) Å (average value) and by a C≡C bond Chapter III. Organometallic Rhodium Complexes with Bulky Phosphine Ligands ! ! ! ! ! ! ! 247 As anticipated, the solid state structure of complex 3a was also confirmed by single crystal X-ray studies. Figure 4 depicts the molecular structure of the cations of 3a. As can be seen, its Rh(I) centre is formally five-coordinate to one of the C=C bonds of COD (C1-C2), and to an η6- aryl ring and the phosphorus atom of the phosphine ligand. The Rh-η2- COD linkage is characterized by Rh—C bonds with length ca. 2.15 Å, comparable to other known Rh(I)-alkene units.16,19,34 The Rh(I)-η6-arene moiety presents, however, relatively long Rh—C bonds, with the exception of the Rh-Cipso contact (Rh1—C15 in Figure 4), which at 2.142 Å is practically identical to the Rh—COD bond distances. The remaining Rh— C bonds to the η6-aryl ring have lengths in the range 2.30-2.35 Å. These separations are similar to, albeit somewhat longer than those reported for other Rh(I)-arene complexes.35 !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! 34 A. Zamorano, N. Rendón, J. E. Valpuesta, E. Álvarez, E. Carmona, Inorg. Chem. 2015, 54, 6573-6581. 35 See for instance: a) R. Uson, L. A. Oro, C. Foces-Foces, F. H. Cano, S. García-Blanco, M. Valderrama, J. Organomet. Chem. 1982, 229, 293-304 ; b) R. Uson, L. A. Oro, C. Foces-Foces, F. H. Cano, A. Vegas, M. Valderrama, J. Organomet. Chem. 1981, 215, 241–253. Chapter III. Organometallic Rhodium Complexes with Bulky Phosphine Ligands ! ! ! ! ! ! ! 248 Figure 4. ORTEP view of the cation of complex 3a; hydrogen atoms are excluded for clarity and thermal ellipsoids are set at 50% level of probability. Selected bond distances (Å) and angles (º): Rh1—P1 = 2.2284(12); Rh1—C1 = 2.162(4); Rh1—C2 = 2.144(4); Rh1—C15 = 2.142(4); Rh1—C16 = 2.313(5); Rh1—C17 = 2.352(5); Rh1—C18 = 2.317(5); Rh1—C19 = 2.350(6); Rh1—C20 = 2.301(5); C15—C16 = 1.432(7); C16—C17 = 1.396(8); C17—C18 = 1.328(10); C18—C19 = 1.397(10); C19—C20 = 1.413(8); C20—C15 = 1.432(7); C1—C2 = 1.389(7); C2—C3 = 1.506(6); C3—C4 = 1.518(7); C4—C5 = 1.463(8); C5—C6 = 1.315(9); C6—C7 = 1.386(10); C7—C8 = 1.454(9); C8—C1 = 1.499(7); C1-Rh1-C2 = 37.64(17); Rh1-C1-C8 = 115.6(4); Rh1-C2-C3 = 115.9(3); C2-C3-C4 = 110.8(4); C1-C8-C7 = 115.5(6). The ethylene adduct 4a, closely related to complex 3a, was cleanly obtained from the reaction of the rhodium dimer [RhCl(C2H4)2]2 with NaBArF in the presence of PMe2ArXyl2 (CH2Cl2, 25 ºC, Scheme 3). Once more, the new compound was characterized by microanalysis and NMR spectroscopy. The 1H and 13C{1H} NMR spectra are completely in accord with the proposed η6-coordination of one of the xylyl substituent of the phosphine. In turn, the ethylene ligand undergoes fast rotation on the NMR time scale at 25 ºC, such that its four hydrogen atoms give rise to a broad 1H NMR resonance at 2.92 ppm, while the 13C nuclei resonate as a doublet at 46.5 ppm (1JCRh = 13 Hz). The NMR parameters recorded for complex Chapter III. Organometallic Rhodium Complexes with Bulky Phosphine Ligands ! ! ! ! ! ! ! 249 4a are very similar to those reported by Hartwig and co-workers for an analogous compound of a dimethylamino-substituted biarylphosphine, PCy2Ar, that presents also η6-arene and κ ,P-coordination of the phosphine.19 Scheme 3. Synthesis of complex 4a. III.2.1.3. Reaction of Complexes [RhCl(COD)(PMe2Ar’)] (2a and 2b), with Carbon Monoxide. Treatment of complexes 2a and 2b with CO (1.5 bar of CO, CH2Cl2, 25 ºC) allowed for the substitution of the bidentated COD by two molecules of CO giving rise to the cis-dicarbonyl derivatives 5a, 5b (Scheme 4), which were completely characterized by microanalysis, IR and NMR spectroscopy. [RhCl(C2H4)2]2 + PMe2ArXyl2 CH2Cl2, 25 ˚C Rh P + BArF- 4a NaBArF Chapter III. Organometallic Rhodium Complexes with Bulky Phosphine Ligands ! ! ! ! ! ! ! 250 ! Scheme 4. Synthesis of complexes 5a-5b. In accord with the cis configuration of the carbonyl ligands, the IR spectra of the two compounds show two ν(CO) bands, corresponding to the symmetric and antisymmetric stretching vibrational modes. For complex 5a, these absorptions appear at 2078 and 1994 cm-1, while for 5b corresponding values are 2070 and 1990 cm-1. The former species gives rise to two 13C resonances at 182.5 (dd, 2JCP = 126, 1JCRh = 59 Hz) and 182.2 (dd, 1JCRh = 74, 2JCP = 17 Hz), which are assigned, respectively, to the carbonyl groups in trans and cis with respect to the phosphorous atom (Figure 5). The 31P{1H} NMR spectrum of 5a exhibits a doublet at -7.1 ppm (1JPRh = 121 Hz). CH2Cl2, 25 ˚C P R R R R Rh Cl R = Me, 2a; iPr, 2b P R R R R Rh Cl OC OC R = Me, 5a; iPr, 5b CO Chapter III. Organometallic Rhodium Complexes with Bulky Phosphine Ligands ! ! ! ! ! ! ! 251 Figure 5. Carbonyl region of the 13C{1H} NMR spectrum of complex 5a (100 MHz, CD2Cl2, 25 ºC). III.2.1.4. Generation of Cationic Carbonyls Derived from Complexes 5a and 5b. Treatment of CH2Cl2 solutions of 5a and 5b with NaBArF cleanly generated the 18-electron cationic monocarbonyls 6a and 6b (Scheme 5). Once again, abstraction of the chloride ligand by the Na+ cation created a vacant coordination site that was occupied by a flanking aryl ring of the phosphine. The latter preferred η6, κ -coordination, and therefore a (2+6)- electron binding mode that caused concomitant dissociation of one of the Chapter III. Organometallic Rhodium Complexes with Bulky Phosphine Ligands ! ! ! ! ! ! ! 252 original carbonyl groups with formation of the formally five-coordinate 18-electron complexes 6a and 6b. Scheme 5. Synthesis of complexes 6a-6b. The IR spectra of the two compounds contain an intense ν(CO) band, that for complex 6a appears at 2018 cm-1, and for 6b around 2012 cm-1. Complexes 6a and 6b were also characterized by NMR spectroscopy. The proposed η6-coordination mode of the xylyl unit is supported by the comparison of the 1H, 13C{1H} and 31P{1H} NMR spectra with those of the related compounds 3a and 4a. In addition, the carbonyl ligand of complex 6a is responsible for a 13C resonance at 183.2 (dd, 1JCRh = 95, 2JCP = 19 Hz) while the 31P{1H} spectrum consists of a doublet at 49.3 ppm (1JPRh = 169 Hz). Complex 6a was further characterized by single crystal X-ray studies (Figure 6). The overall structure is similar to that previously discussed for complex 3a. The molecules of 6a have a Rh1—P1 bond essentially identical (2.2338(17) Å) to the Rh—P bond of 3a and to those in related complexes containing η6, κ 1-arene-phosphine ligands.16,19 There are some R = Me, 6a; iPr, 6b CH2Cl2, 25 ˚C P R R R R Rh Cl OC OC R = Me, 5a; iPr, 5b Rh OC P + BArF- R R R R NaBArF Chapter III. Organometallic Rhodium Complexes with Bulky Phosphine Ligands ! ! ! ! ! ! ! 253 small differences in the Rh-η6-arene linkages of complexes 3a and 6a, as in the latter the Rh—Carene contacts are somewhat longer. Similar to 3a, the Rh—Cipso bond exhibits the shortest separation (Rh1—C8 = 2.163(5) Å), but the remaining Rh—Carene bonds span over the range ca. 2.31-2.39 Å. The Rh—CO bond features regular metrics (see Figure 6). Figure 6. ORTEP view of the cation of complex 6a; hydrogen atoms are excluded for clarity and thermal ellipsoids are set at 50% level of probability. Selected bond distances (Å) and angles (º): Rh1—P1 = 2.2338(17); Rh1—C1 = 1.846(6); Rh1—C8 = 2.163(5); Rh1—C9 = 2.312(7); Rh1—C10 = 2.379(9); Rh1—C11 = 2.360(9); Rh1—C12 = 2.395(7); Rh1—C13 = 2.325(6); P1—C24 = 1.789(8); P1—C25 = 1.785(6); P1—C2 = 1.862(5); O1—C1 = 1.145(8); C8—C9 = 1.447(8); C9—C10 = 1.415(8); C10—C11 = 1.402(11); C11—C12 = 1.381(11); C12—C13 = 1.411(8); C13—C8 = 1.427(8); C1-Rh1-P1 = 88.7(2); O1-C1-Rh1 = 173.9(6); C2-P1-Rh1 = 103.7(2). The cationic complex 6a underwent some interesting rearrangements when it was reacted with CO under a pressure of 6 bar. The changes were monitored by 13C{1H} NMR spectroscopy at variable temperature (from 25 to -60 ºC) and are represented in Scheme 6. As can be seen, the CO- induced reactivity involved the attainment of a fast equilibrium on the Chapter III. Organometallic Rhodium Complexes with Bulky Phosphine Ligands ! ! ! ! ! ! ! 254 laboratory time scale between the starting monocarbonyl complex 6a and a tricarbonyl species, 7a, the latter with monodentate, κ 1-P-coordination of the terphenyl phosphine ligand. Such an equilibrium is naturally temperature dependent, with an increase in temperature favouring complex 6a with the chelating η6, κ 1-arene-phosphine coordination, relative to complex 7a of the monodentate κ 1-phosphine (vide infra). But in addition, the variable temperature 13C NMR studies to be discussed next, uncovered that the tricarbonyl derivative 7a equilibrated on the NMR time scale with an unobserved dicarbonyl species 8a. In the latter, the unsaturated Rh(I) centre is proposed to contain two coordinated molecules of CO and to participate in a secondary interaction with the ipso carbon atom of a flanking aryl ring. Scheme 6. Complexes 6a, 7a and 8a are equilibrated under a CO atmosphere (6 bar, CD2Cl2, 25 ºC to -60 ºC). Figure 7 contains 13C{1H} NMR spectra of CD2Cl2 solutions of complex 6a recorded at 25, -40 and -60 ºC, under 6 bar of CO, in the carbonyl and aliphatic regions of the spectrum (roughly 185-176 and 24-16 ppm, respectively). With reference to the room temperature spectrum, the monocarbonyl 6a exhibits the expected doublet-of-doublet carbonyl 6a 7a Rh OC P + BArF- P Rh CO OC OC + BArF- 8a (not observed) P Rh CO OC + + 2 CO - 2 CO + CO - CO 25 ºC fast (lab. time scale) 25 ºC very fast (NMR time scale) BArF- Chapter III. Organometallic Rhodium Complexes with Bulky Phosphine Ligands ! ! ! ! ! ! ! 255 resonance centred at 183.2 ppm, the PMe2 doublet at 19.1 ppm (d, 1JCP = 37 Hz) and the Me(Xyl) singlets with δ 22.0 and 20.3 ppm. In addition, there is a broad hump centred at ca. 182.1 ppm and a singlet at 22.4 ppm that are attributed to the CO ligands and Me(Xyl) groups respectively of the purported tricarbonyl 7a. The signal due to the PMe2 groups of the phosphine is very broad and can be conjectured at 19.5 ppm, practically hidden into the base-line. Upon cooling, this signal becomes clearly discernible and appears at 18.5 ppm (d, 1JCP = 37 Hz) in the -60 ºC spectrum. At the latter temperature, the broad signal of the CO ligands of 7a centred at ca. 182.1 ppm, resolves into two doublet-of-doublet resonances in a ca. 2:1 ratio, observed at 180.6 (1JCRh = 69, 2JCP = 16 Hz) and 178.8 ppm (1JCRh = 51, 2JCP = 92 Hz), attributable respectively to two cis and one trans carbonyl groups, relative to the phosphine ligand. In accordance with these findings, the 31P{1H} NMR spectrum (Figure 8) at 25 ºC shows the expected doublet for 6a with δ 49.3 together with a broad signal at -2.30 ppm, which converts into a sharp doublet at -1.21 ppm (1JPRh = 91 Hz) at -60 ºC. Chapter III. Organometallic Rhodium Complexes with Bulky Phosphine Ligands ! ! ! ! ! ! ! 256 Figure 7. Variable temperature 13C{1H} NMR spectra, in the carbonyl and aliphatic regions, of complex 6a under 6 bar of CO (100 MHz, CD2Cl2, 25 ºC to - 60 ºC). The above data are in agreement with the already anticipated temperature-dependent equilibrium between complexes 6a and 7a, under 6 bar of CO (Scheme 6). At -60 ºC the two complexes exist in almost 1:1 ratio. Notwithstanding these considerations, the broadness of the 13C{1H} resonances recorded for 7a at 25 ºC suggested the additional participation of this species in a second equilibrium, now on the NMR time scale. We propose that this equilibrium includes an unobserved dicarbonyl 8a Chapter III. Organometallic Rhodium Complexes with Bulky Phosphine Ligands ! ! ! ! ! ! ! 263 ! Scheme 9. Synthesis of the carbonyl adducts 11b-11e by the reaction of complexes 9b-9e with NaBArF in the presence of CO (1.5 bar, CH2Cl2, 25 ºC). As observed previously for complex 9a, when the reaction of 9b-9e with NaBArF was carried out in CH2Cl2 in the absence of a sufficiently good donor, the new compounds 12b-12e, in which the phosphine ligand displays the unusual κ,P,η3-pseudoallyl binding through the phosphorus atom and the metallated Xyl’ ring, were obtained. As expected, these complexes reacted readily with CO to give the carbonyls 11b-11e described above. R = Me, 11b; OMe, 11c; F, 11d 11e CO, NaBArF CH2Cl2, 25 ºC CO, NaBArF BArF- Rh PCl CH2 Et Xyl 9e Rh PCl CH2 Me R R R = Me, 9b; OMe, 9c; F, 9d Rh PCO CH2 Me R R BArF- Rh PCO CH2 Et Xyl CH2Cl2, 25 ºC Chapter III. Organometallic Rhodium Complexes with Bulky Phosphine Ligands ! ! ! ! ! ! ! 264 ! Scheme 10. Synthesis of complexes 12b-12e and their reaction with carbon monoxide (CH2Cl2, 25 ºC). The pseudo-allylic compounds 12b-12e were characterized by NMR spectroscopy. Figure 9 compares the room temperature 1H NMR spectra of the four complexes. Similar to the already reported complex 12a,30d they exhibit a fluxional behaviour in solution that exchanges the roles of the metallated and non-metallated xylyl rings. Using 12b as a representative example, the diastereotopic hydrogen atoms of the rhodium-bound CH2 group feature divergent chemical shifts, as they resonate at 1.29 (ddd, 3JHP = 13.9, 2JHH = 4.0, 2JHRh = 0.7 Hz) and 2.91 ppm (dt, 2JHH = 4.0, 2JHRh = 3JHP = 1.3 Hz). In the 13C{1H} NMR spectrum the corresponding signal was recorded at 41.5 ppm (dd, 2JCP = 15, 1JCRh = 2 Hz). It is worth noting that the change in the coordination mode of the metallated phosphine from the carbonyl complexes 11 to the NaBArFCH2 P Rh Me R BArF - R Rh PCl CH2 Et Xyl Rh PCl CH2 Me R R CH2 P Rh Et 12e BArF - 9b-9d R = Me, 12b; OMe, 12c; F, 12d 9e NaBArF Rh PCO CH2 Me R R Rh PCO CH2 Et CO R = Me, 11b; OMe, 11c; F, 11d 11e CO CH2Cl2, 25 ºC BArF - BArF - BArF - BArF - CH2Cl2, 25 ºC CH2Cl2, 25 ºC CH2Cl2, 25 ºC Chapter III. Organometallic Rhodium Complexes with Bulky Phosphine Ligands ! ! ! ! ! ! ! 265 pseudo-allylic derivatives 12 is characterized by a distinct shift of about 50 ppm to lower frequencies of the 31P{1H} resonance, since in the latter compounds this signal appears at -15.7- -17.5 ppm for 12b-12d, and at -4.4 ppm for 12e. The structure proposed for these complexes was further confirmed by X-ray studies performed with single crystals of 12d and 12e. Figure 10 shows ORTEP diagrams for the cations of these compounds. The coordinated atoms of the metallated phosphine ligand of complex 12d, with the κ,P,η3-coordination mode, that is, P(1a), C(11a), C(16a), and C(18a), form an essentially planar arrangement which is nearly parallel to the C5Me5 ring plane (dihedral angle 8.1°). Accordingly, the Rh—C distances to C(11a), 2.252(9) Å; C(16a), 2.220(8) Å; and C(18a), 2.241(11) Å are clearly bonding, while for 9b (Figure 5), which presents the more common κ2-P,C coordination mode, only the Rh—C(1) distance of 2.101(8) Å is bonding. In the latter compound the Rh—C(2) and Rh— C(3) separations are 3.09 and 3.27 Å, respectively. Chapter III. Organometallic Rhodium Complexes with Bulky Phosphine Ligands ! ! ! ! ! ! ! 266 Figure 9. 1H NMR spectra (400 MHz, CD2Cl2, 25 ºC) of complexes 12b-12e. Chapter III. Organometallic Rhodium Complexes with Bulky Phosphine Ligands ! ! ! ! ! ! ! 267 !!!!!!!!!!!! Figure 10. ORTEP view of the cations of complexes 12d (left) and 12e (right); hydrogen atoms are excluded for clarity and thermal ellipsoids are set at 50% level of probability. Selected bond distances (Å) and angles (º) for 12d: Rh1a— P1a = 2.269(7); Rh1a—C11a = 2.252(9); Rh1a—C16a = 2.220(8); Rh1a—C18a = 2.241(11); C11a—C12a = 1.438(13); C12a—C13a = 1.34(2); C13a—C14a = 1.46(2); C14a—C15a = 1.335(18); C15a—C16a = 1.420(14); C11a—C16a = 1.444(12); C16a—C18a = 1.429(16); P1a—C11a = 1.791(12); C11a-C16a-C18a = 124.7(10); P1a-C11a-C16a = 111.9(7). Selected bond distances (Å) and angles (º) for 12e: Rh1—P1 = 2.2577(14); Rh1—C13 = 2.289(5); Rh1—C18 = 2.220(5); Rh1—C20 = 2.141(5); C17—C18 = 1.428(8); C16—C17 = 1.347(9); C15—C16 = 1.416(9); C14—C15 = 1.355(8); C13—14 = 1.439(8); C13—C18 = 1.449(7); C18—C20 = 1.446(8); P1—C13 = 1.815(6); C13-C18-C20 = 118.4(5); P1-C13- C18 = 110.7(4). III.2.2.3. Reaction of Complexes 12b-12e with Hydrogen. Previously, our group reported on the reaction of complex 12a with H2. Specifically, and even if 1H and 31P{1H} NMR studies indicated no observable reaction after exposure of CD2Cl2 solutions of this species to H2 (1.5 bar) at 25 ºC, pressurizing with 1.5 bar of D2 instead of H2 produced the fast deuteration (10 minutes) of the methyl and methylene C—H bonds of the two xylyl rings (Scheme 11). With the aim of ascertaining this H/D Chapter III. Organometallic Rhodium Complexes with Bulky Phosphine Ligands ! ! ! ! ! ! ! 268 exchange mechanism, the reaction with H2 was studied at -80 ºC, when the formation of small quantities of a cationic agostic hydride species, namely 13a, in equilibrium with the starting material (Scheme 12), became apparent. Scheme 11. Deuteration of the methylene and all the methyl groups of the xylyl rings of complexes 12a-12e under a D2 atmosphere (1.5 bar, 25 ºC, 10 minutes). To complete this study, the reactions of complexes 12b-12e with H2 were carried out. Similar to the parent complex 12a, no reaction with H2 (1 bar) was observed at room temperature for any of these compounds, although the deuteration of the C—H bonds of the methylene and methyl groups of the xylyl rings also took place under an atmosphere of D2. Thus, when the temperature was lowered to -80 ºC the characteristic signals of D2 CD2Cl2 D3C CD2 P Rh Me CD3 CD3 FF R = H, 12a-d11; Me, 12b-d11; OMe, 12c-d11; F, 12d-d11 BArF- CH2 P Rh Me R R CH2 P Rh Et 12e R = H, 12a; Me, 12b; OMe, 12c; F, 12d BArF- BArF- D2 CD2Cl2 D3C CD2 P Rh Et CD3 CD3 BArF- 12e-d11 Chapter III. Organometallic Rhodium Complexes with Bulky Phosphine Ligands ! ! ! ! ! ! ! 269 the cationic agostic hydrides related with 13a, in equilibrium with the starting material, and with the exception of the methoxy-substituted 13c, were observed (Scheme 12). Once more, upon cooling at -80 ºC solutions of complexes 12b-12e in the presence of H2, 1H NMR resonances characteristic of cationic agostic hydrides analogous to 13a were recorded, with the only exception of the para-methoxy substituted compounds 12c that provided no detectable concentrations of the expected hydride 13c. While for the originally studied 12a/13a couple the ratio measured was ca. 90:10, for the remaining systems were of roughly 98:2 (12b:13b), 83:17 (12c:13c) and 95:5 (12e:13e). All reactions were performed under indetical experimental conditions. Although differences among them were small, it appears that for the series of the PMe(Xyl’)2 complexes the tendency to generate the cationic agostic structure increases in the order OMe>Me>H>F, i.e. upon decreasing the overall donor capacity of the phosphine. Chapter III. Organometallic Rhodium Complexes with Bulky Phosphine Ligands ! ! ! ! ! ! ! 270 ! Scheme 12. Established equilibrium between the cationic agostic hydride, 13, and complexes 12 upon the reaction of the latter with H2 (1 bar, CD2Cl2, -80 ºC). Figure 11 represents the low-temperature (-80 ºC) 31P{1H} NMR spectrum of complex 13d, as a representative example of the family of agostic hydrides, 13. It is evident the appearance of a new doublet at much lower field (27.6 ppm; d, 1JPRh = 141 Hz), clearly indicating the change in the coordination of the phosphine from the formally tridentate κ,P,η3- binding fashion in 12d to the κ,P-agostic coordination in 13d. Formation of the hydride complex 13d is also evinced in the 1H NMR spectrum (Figure 12), by a broad multiplet centred at -9.23 ppm corresponding to the hydride ligand. In addition, a broad singlet with relative intensity corresponding to 3H atoms compared to the signal of the hydride, is recorded with δ 0.02 for the agostic methyl group of the xylyl ring. The Rh PH CH3 Et Xyl Rh PH CH3 Me R R CH2 P Rh Me R R CH2 P Rh Et 12e R = H, 12a; Me, 12b; F, 12d R = H, 12a; Me, 13b; F, 13d 13e BArF- BArF- BArF- BArF- H2 H2 CD2Cl2, -80 ºC CD2Cl2, -80 ºC Chapter III. Organometallic Rhodium Complexes with Bulky Phosphine Ligands ! ! ! ! ! ! ! 271 unusual chemical shift of this signal is in accord with the proposed participation in an agostic interaction with the rhodium centre. Figure 11. 31P{1H} NMR spectra (200 MHz, CD2Cl2, -80 ºC) of the established equilibrium between the cationic agostic hydride, 13d, and complex 12d upon the reaction of the latter with H2 (1 bar). Chapter III. Organometallic Rhodium Complexes with Bulky Phosphine Ligands ! ! ! ! ! ! ! 272 Figure 12. 1H NMR spectra (500 MHz, CD2Cl2, -80 ºC) of the equilibrium established between the cationic agostic hydride, 13d, and complex 12d upon reaction of the latter with H2 (1 bar). III.2.2.4. Deuteration of Hydrosilanes and Hydrosilylation of Aromatic Ketones Catalyzed by Complexes 12b-12e. The title reactions were extensively studied by our group for the parent complex 12a, which proved to be a very active catalyst.30c,30d,36 Since the results discussed in the previous sections for complexes 12b-12e and some of their derivatives, like the carbonyls 11b-11e, revealed similar electronic and steric properties compared to 12a, we decided to study only two silanes, SiHEt3 and SiH(SiMe3)3, for both catalytic H/D exchanges and Chapter III. Organometallic Rhodium Complexes with Bulky Phosphine Ligands ! ! ! ! ! ! ! 279 13C{1H} NMR (75 MHz, 25 ºC, CD2Cl2) δ: 146.3 (d, 2JCP = 9 Hz, C2), 142.2 (d, 3JCP = 4 Hz, C3), 137.4 (C4), 130.9 (d, 3JCP = 7 Hz, CHa), 130.6 (d, 1JCP = 35 Hz, C1), 130.2 (d, 4JCP = 2 Hz, CHb), 128.1 (CHd), 127.9 (CHe), 101.1 (dd, 1JCRh = 14, 2JCP = 8 Hz, CHf), 69.2 (d, 1JCRh = 14 Hz, CHe), 33.5, 28.6 (d, 2JCRh = 2 Hz, CH2), 22.4 (ArMe), 13.2 (d, 1JCP = 25 Hz, PMe2). 31P{1H} NMR (120 MHz, 25 ºC, CD2Cl2) δ: -5.1 (d, 1JPRh = 144 Hz). Chapter III. Organometallic Rhodium Complexes with Bulky Phosphine Ligands ! ! ! ! ! ! ! 280 Complex 2b: ! Anal. Calc. for C40H55ClPRh: C, 68.1; H, 7.9. Found: C, 68.4; H, 8.2. 1H NMR (500 MHz, 25 ºC, CD2Cl2) δ: 7.43 (t, 2 H, 3JHH = 7.9 Hz, 2 Hd), 7.39 (td, 1 H, 3JHH = 7.6, 5JHP = 1.7 Hz, Hb), 7.32 (d, 4 H, 3JHH = 7.9 Hz, 4 Hc), 7.14 (dd, 2 H, 3JHH = 7.6, 4JHP = 2.6 Hz, 2 Ha), 4.90 (br s, 2 H, 2 Hf), 2.65 (br s, 2 H, 2 He), 2.86 (br s, 4 H, 4 CH(CH3)2), 2.47, 2.18, 1.76, 1.64 (m, 8 H, 4 CH2), 1.44, 0.99 (d, 24 H, 3JHH = 6.9 Hz, 4 CH(CH3)2), 1.09 (d, 6 H, 2JHP = 7.9 Hz, PMe2). 13C{1H} NMR (125 MHz, 25 ºC, CD2Cl2) δ: 147.0 (C4), 143.4 (d, 2JCP = 9 Hz, C2), 139.4 (d, 3JCP = 3 Hz, C3), 132.6 (d, 3JCP = 7 Hz, CHa), 130.0 (d, 1JCP = 26 Hz, C1), 128.5 (CHd), 126.8 (d, 4JCP = 4 Hz, CHb), 122.8 (CHc), 98.6 (dd, 1JCRh = 14, 2JCP = 8 Hz, CHf), 69.7 (d, 1JCRh = 14 Hz, CHe), 32.6 (d, 2JCRh = 4 Hz, CH2), 30.8 (CH(CH3)2), 28.6 (d, 2JCRh = 2 Hz, CH2), 25.9, 22.2 (CH(CH3)2), 14.4 (d, 1JCP = 25 Hz, PMe2). 31P{1H} NMR (200 MHz, 25 ºC, CD2Cl2) δ: -6.9 (d, 1JPRh = 145 Hz).! P 12 2 3 3 4 4 4 4 Rh Cl HaHb Ha Hc Hd Hc HcHd Hc He He Hf Hf Chapter III. Organometallic Rhodium Complexes with Bulky Phosphine Ligands ! ! ! ! ! ! ! 281 Synthesis and characterization of complex 3a. To a solid mixture of complex 2a (0.08 mmol) and NaBArF (0.08 mmol), placed in a thick-wall ampoule, was added 5 mL of CH2Cl2. The resulting solution was stirred for 10 min at room temperature, filtered and the volatiles evaporated under reduced pressure to obtain complex 3a as an orange powder in ca. 95% yield. This species can be recrystallized by slow diffusion at -20 ºC of pentane into a CH2Cl2 solution (2:1 by vol.). ! Anal. Calc. for C64H51BF24PRh: C, 54.1; H, 3.6. Found: C, 54.4; H, 3.4. 1H NMR (400 MHz, 25 ºC, CD2Cl2) δ: 7.82, 7.57, 7.30, 7.20, 6.80, 5.88 (br s, 9 H, Har), 5.53 (s, 2 H, H9), 3.44 (s, 2 H, H8), 2.44, 2.10 (m, 8 H, CH2), 2.16, 2.01 (br s, 6 H each, ArMe), 1.23 (d, 6 H, 2JHP = 11.3 Hz, PMe2). 1H NMR (400 MHz, 0 ºC, CD2Cl2) δ: 7.81 (detected by COSY, Hb), 7.59 (m, 1 H, Ha), 7.30 (t, 1 H, 3JHH = 7.5 Hz, Hg), 7.27 (dd, 1 H, 3JHH = 7.4 Hz, 4JHP = 7.4 Hz, Hc), 7.18 (d, 2 H, 3JHH = 7.4 Hz, 2 Hf), 6.75 (d, 2 H, 3JHH = Rh P 15 2 6 77 3 4 4 + BArF- Meα MeαMeβ Meβ Hd He Hd HaHb Hc Hf Hg Hf Hh Hi Hi Hh Chapter III. Organometallic Rhodium Complexes with Bulky Phosphine Ligands ! ! ! ! ! ! ! 282 6.4 Hz, 2 Hd), 5.81 (t, 1 H, 3JHH = 6.6 Hz, He), 5.55 (s, 2 H, 2 Hi), 3.38 (s, 2 H, Hh), 2.43, 2.07 (m, 8 H, 4 CH2), 2.13 (s, 6 H, 2 Meα), 1.98 (s, 6 H, 2 Meβ), 1.20 (d, 6 H, 2JHP = 11.3 Hz, PMe2). 13C{1H} NMR (100 MHz, 0 ºC, CD2Cl2) δ: 146.8 (C2/5), 142.6 (d, 2JCP = 21 Hz, C2/5), 137.8 (d, 1JCP = 50 Hz, C1), 137.8 (C6), 136.3 (C7), 133.5 (CHb), 132.3 (d, 3JCP = 6 Hz, CHc), 132.3 (CHi), 128.6 (CHg), 127.8 (CHf), 127.7 (d, 3JCP = 15 Hz, CHa), 120.5 (C4), 116.1 (C3), 112.1 (CHd), 97.1 (d, 1JCRh = 10 Hz, CHe), 74.0 (d, 1JCRh = 13 Hz, CHh), 35.1, 31.7 (CH2 COD), 21.1 (Meβ), 19.5 (Meα), 13.6 (d, 1JCP = 33 Hz, PMe2). 31P{1H} NMR (160 MHz, 0 ºC, CD2Cl2) δ: 48.1 (d, 1JPRh = 192 Hz).! Chapter III. Organometallic Rhodium Complexes with Bulky Phosphine Ligands ! ! ! ! ! ! ! 283 Synthesis and characterization of complex 4a. A solid mixture of the rhodium dimer, [RhCl(C2H2)2]2, (0.2 mmol), the phosphine 1a (0.40 mmol) and NaBArF (0.04 mmol), placed in a Schlenk flask, was dissolved in CH2Cl2 (6 mL). The solution was stirred for 1 hour at room temperature, and the solvent was then evaporated under reduced pressure to obtain complex 4a in ca. 90% yield. This complex can be recrystallized by slow diffusion at -20 ºC of pentane into a CH2Cl2 solution (2:1 by vol.). ! Anal. Calc. for C58H43BF24PRh: C, 52.0; H, 3.2. Found: C, 52.0; H, 3.5. 1H NMR (500 MHz, 25 ºC, CD2Cl2) δ: 7.84 (td, 1 H, 3JHH = 7.6, 5JHP = 2.4 Hz, Hb), 7.65 (ddd, 1 H, 3JHH = 7.7, 4JHP = 2.3, 4JHRh = 1.3 Hz, Ha), 7.21 (t, 1 H, 3JHH = 7.7 Hz, Hg), 7.30 (m, 1 H, Hc), 7.19 (d, 2 H, 3JHH = 7.3 Hz, 2 Hf), 6.96 (d, 2 H, 3JHH = 6.6 Hz, 2 Hd), 5.54 (td, 1 H, 3JHH = 6.6, 3JHP = 2.3 Hz, He), 2.92 (br s, 4 H, H2C=CH2), 2.18 (s, 6 H, 2 Meα), 1.99 (s, 6 H, 2 Meβ), 1.18 (dd, 6 H, 2JHP = 11.5, 3JHRh = 1.4 Hz, PMe2). Rh P 15 2 6 77 3 4 4 + BArF- Meα MeαMeβ Meβ Hd He Hd HaHb Hc Hf Hg Hf NOE Chapter III. Organometallic Rhodium Complexes with Bulky Phosphine Ligands ! ! ! ! ! ! ! 284 13C{1H} NMR (125 MHz, 25 ºC, CD2Cl2) δ: 147.5 (C5), 142.8 (d, 2JCP = 20 Hz, C2), 138.8 (d, 1JCP = 52 Hz, C1), 137.8 (C6), 133.9 (d, 4JCP = 2Hz, CHb), 132.8 (d, 3JCP = 6 Hz, CHc), 129.0 (CHg), 128.1 (CHf), 128.0 (CHa), 117.9 (C4, C7), 116.5 (C3), 109.1 (CHd), 94.7 (d, 1JCRh = 12 Hz, CHe), 46.5 (d, 1JCRh = 13 Hz, H2C=CH2), 21.3 (Meβ), 19.6 (Meα), 13.9 (d, 1JCP = 33 Hz, PMe2). 31P{1H} NMR (200 MHz, 25 ºC, CD2Cl2) δ: 48.1 (d, 1JPRh = 185 Hz). ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! Chapter III. Organometallic Rhodium Complexes with Bulky Phosphine Ligands ! ! ! ! ! ! ! 285 Synthesis and characterization of complexes 5a and 5b. A solution of the corresponding complex 2 (0.08 mmol) in CH2Cl2 (5mL), placed in a thick-wall ampoule, was stirred for 10 min at room temperature under 1.5 bar of CO. The solvent was evaporated under reduced pressure to obtain complexes 3a and 3b as yellow powders in ca. 90% yield. They can be recrystallized by slow diffusion at -20 ºC of pentane into a CH2Cl2 solution (2:1 by vol.). Complex 5a: IR (Nujol): 2078, 1994 cm-1. Anal. Calc. for C26H27ClO2PRh: C, 57.7; H, 5.0. Found: C, ; H, . 1H NMR (400 MHz, 25 ºC, CD2Cl2) δ: 7.63 (td, 1 H, 3JHH = 7.6, 5JHP = 1.8 Hz, Hb), 7.30 (t, 2 H, 3JHH = 7.5 Hz, 2 Hd), 7.21 (d, 4 H, 3JHH = 7.6 Hz, 4 Hc), 7.12 (dd, 2 H, 3JHH = 7.6, 4JHP = 3.1 Hz, 2 Ha), 2.18 (s, 12 H, 4 ArMe), 1.32 (dd, 6 H, 2JHP = 9.2, 3JHRh = 1.3 Hz, PMe2). 13C{1H} NMR (100 MHz, 25 ºC, CD2Cl2) δ: 182.5 (dd, 2JCP = 126, 1JCRh = 59 Hz, C6O), 182.2 (dd, 1JCRh = 74, 2JCP = 17 Hz, C5O), 146.6 (d, 2JCP = 10 Hz, C2), 141.3 (d, 3JCP = 5 Hz, C3), 136.4 (C4), 131.3 (d, 4JCP = 2 Hz, CHb), 130.9 (d, 3JCP = 7 Hz, CHa), 128.1 (CHd), 128.0 (CHc), 127.7 (d, 1JCP = 41 Hz, C1), 21.8 (ArMe), 16.3 (d, 1JCP = 32 Hz, PMe2). 31P{1H} NMR (160 MHz, 25 ºC, CD2Cl2) δ: -7.1 (d, 1JPRh = 121 Hz).! P 12 2 3 3 4 4 4 4 Rh Cl HaHb Ha Hc Hd Hc HcHd Hc OC5 OC6 Chapter III. Organometallic Rhodium Complexes with Bulky Phosphine Ligands ! ! ! ! ! ! ! 286 Complex 5b: ! IR (Nujol): 2070 cm-1, 1990 cm-1. Anal. Calc. for C34H43ClO2PRh: C, 62.5; H, 6.6. Found: C, 62.4; H, 6.6. 1H NMR (400 MHz, 25 ºC, CD2Cl2) δ: 7.51 (td, 1 H, 3JHH = 7.6, 5JHP = 1.8 Hz, Hb), 7.44 (t, 2 H, 3JHH = 7.7 Hz, 2 Hd), 7.31 (d, 4 H, 3JHH = 7.7 Hz, 4 Hc), 7.27 (dd, 2 H, 3JHH = 7.8, 4JHP = 3.0 Hz, 2 Ha), 2.75 (hept, 4 H, 3JHH = 6.8 Hz, 4 CH(CH3)2), 1.42, 1.03 (d, 24 H, 3JHH = 6.7 Hz, 4 CH(CH3)2), 1.25 (dd, 6 H, 2JHP = 9.5, 3JHRh = 1.3 Hz, PMe2). 13C{1H} NMR (100 MHz, 25 ºC, CD2Cl2) δ: 182.7 (dd, 2JCP = 127, 1JCRh = 59 Hz, C6O), 182.3 (dd, 1JCRh = 57, 2JCP = 17 Hz, C5O), 147.1 (C4), 144.3 (d, 2JCP = 10 Hz, C2), 138.9 (d, 3JCP = 4 Hz, C3), 133.1 (d, 3JCP = 8 Hz, CHa), 129.7 (d, 1JCP = 51 Hz, C1), 129.0 (CHd), 128.1 (d, 3JCP = 2 Hz, CHb), 123.2 (CHc), 31.0 (CH(CH3)2), 25.8, 22.9 (CH(CH3)2), 16.6 (d, 1JCP = 33 Hz, PMe2). 31P{1H} NMR (160 MHz, 25 ºC, CD2Cl2) δ: -4.1 (d, 1JPRh = 121 Hz).! P 12 2 3 3 4 4 4 4 Rh Cl HaHb Ha Hc Hd Hc HcHd Hc OC6 OC5 Chapter III. Organometallic Rhodium Complexes with Bulky Phosphine Ligands ! ! ! ! ! ! ! 287 Synthesis and characterization of complexes 6a and 6b. To a solid mixture of the corresponding chloride precursor 2 (0.08 mmol) and NaBArF (0.08 mmol), placed in a thick-wall ampoule, was added 5 mL of CH2Cl2 and the resulting solution stirred for 10 min at room temperature under 1.5 bar of CO. After filtering, the solvent was evaporated under reduced pressure and the solid obtained washed with pentane (2×10 mL). Complexes 6a and 6b were isolated as orange powders in ca. 95% yield, which can be recrystallized by slow diffusion at -20 ºC of pentane into a CH2Cl2 solution (2:1 by vol.). Complex 6a: ! IR (Nujol): 2018 cm-1. Anal. Calc. for C57H39BF24OPRh: C, 51.1; H, 2.9. Found: C, 51.5; H, 2.6. 1H NMR (500 MHz, 25 ºC, CD2Cl2) δ: 7.88 (td, 1 H, 3JHH = 7.6, 5JHP = 2.6 Hz, Hb), 7.59 (d, 1 H, 3JHH = 7.8 Hz, Ha), 7.36 (m, 2 H, Hg, Hc), 7.23 (d, 2 Rh OC P 15 2 6 77 3 4 4 + BArF- Meα MeαMeβ Meβ Hd He Hd HaHb Hc Hf Hg Hf NOE Chapter III. Organometallic Rhodium Complexes with Bulky Phosphine Ligands ! ! ! ! ! ! ! 288 H, 3JHH = 7.7 Hz, 2 Hf), 7.09 (d, 2 H, 3JHH = 6.9 Hz, 2 Hd), 6.30 (t, 1 H, 3JHH = 6.7 Hz, He), 2.17 (s, 6 H, 2 Meα) 2.01 (s, 6 H, 2 Meβ), 1.56 (d, 6 H, 2JHP = 11.9 Hz, PMe2). 13C{1H} NMR (125 MHz, 25 ºC, CD2Cl2) δ: 183.2 (dd, 1JCRh = 95, 2JCP = 19 Hz, CO), 148.5 (C2/5), 142.8 (d, 2JCP = 19 Hz, C5/2), 138.4 (d, 1JCP = 49 Hz, C1), 137.7 (C7), 135.2 (CHb), 133.8 (d, 3JCP = 7 Hz, CHc), 130.5 (CHg), 128.9 (CHf), 128.8 (d, 3JCP = 5 Hz, CHa), 126.5 (C6), 123.1 (C4), 115.6 (C3), 110.3 (CHd), 97.9 (d, 1JCRh = 8 Hz, CHe), 22.0 (Meβ), 20.3 (Meα), 19.1 (d, 1JCP = 37 Hz, PMe2). 31P{1H} NMR (200 MHz, 25 ºC, CD2Cl2) δ: 49.3 (d, 1JPRh = 169 Hz). Chapter III. Organometallic Rhodium Complexes with Bulky Phosphine Ligands ! ! ! ! ! ! ! 295 Minor diastereomer: 1H NMR (400 MHz, 25 ºC, CDCl3) δ: 6.76 (s, 1 H, Ha), 6.66 (s, 1 H, Hd), 6.44 (s, 1 H, Hc), 6.41 (s, 1 H, Hb), 3.77 (s, 3 H, Meε), 3.73 (s, 3 H, Meδ), 3.64 (dt, 1 H, 2JHH = 12.9, 2JHRh = 3JHP = 2.5 Hz, RhCHH), 3.35 (dd, 1 H, 2JHRh = 3.5, 2JHH = 12.9 Hz, RhCHH), 2.55 (s, 3 H, Meγ), 2.32 (d, 3 H, 2JHP = 10.3 Hz, PMe), 1.92 (s, 3 H, Meα), 1.50 (s, 3 H, Meβ), 1.46 (d, 15 H, 4JHP = 2.5 Hz, C5Me5). 13C{1H} NMR (100 MHz, 25 ºC, CDCl3) δ: 160.7 (C4), 159.7 (C7), 159.1 (d, 2JCP = 35 Hz, C1), 143.6 (d, 2JCP = 10 Hz, C6), 141.6 (d, 2JCP = 8 Hz, C8), 139.9 (C3), 130.3 (dd, 1JCP = 58, 2JCRh = 2 Hz, C2), 123.6 (d, 1JCP = 38 Hz, C5), 115.1 (d, 3JCP = 8 Hz, CHd), 115.0 (d, 3JCP = 8 Hz, CHc), 114.8 (d, 3JCP = 7 Hz, CHb), 109.9 (d, 3JCP = 18 Hz, CHa) 98.0 (t, 1JCRh = 2JCP = 4 Hz, C5Me5), 54.9 (Meδ, Meε), 31.8 (dd, 1JCRh = 24, 2JCP = 7 Hz, RhCH2), 26.1 (d, 3JCP = 5 Hz, Meγ), 23.5 (d, 3JCP = 7 Hz, Meβ), 22.7 (d, 1JCP = 34 Hz, PMe), 20.4 (d, 3JCP = 2 Hz, Meα), 8.7 (C5Me5). 31P{1H} NMR (160 MHz, 25 ºC, CDCl3) δ: 40.0 (d, 1JPRh = 156 Hz). Chapter III. Organometallic Rhodium Complexes with Bulky Phosphine Ligands ! ! ! ! ! ! ! 296 Complex 9d: Anal. Calc. for C27H33ClF2PRh: C, 57.4; H, 5.9. Found: C, 57.2; H, 6.2. 1H NMR (400 MHz, 25 ºC, CDCl3) δ: 6.94 (d, 1 H, 3JHF = 9.5 Hz, Ha), 6.87 (dt, 1 H, 3JHF = 9.5, 4JHP = 4JHH = 2.6 Hz, Hc/d), 6.65 (dt, 1 H, 3JHF = 9.3, 4JHP = 4JHH = 2.6 Hz, Hd/c), 6.58 (d, 1 H, 3JHF = 9.6 Hz, Hb), 3.52 (dt, 1 H, 2JHH = 13.5, 2JHRh = 3JHP = 3.0 Hz, RhCHH), 3.35 (dd, 1 H, 2JHH = 13.5, 2JHRh = 3.2 Hz, RhCHH), 2.60 (s, 3 H, Meβ/γ), 2.19 (d, 3 H, 2JHP = 10.1 Hz, PMe), 1.94 (s, 3 H, Meα), 1.50 (s, 3 H, Meβ/γ), 1.42 (d, 15 H, 4JHP = 2.5 Hz, C5Me5). 13C{1H} NMR (100 MHz, 25 ºC, CDCl3) δ: 163.8 (dd, 1JCF = 251, 4JCP = 2 Hz, C4), 162.6 (dd, 1JCF = 25, 4JCP = 2 Hz, C7), 159.9 (dd, 2JCP = 36, 3JCF = 8 Hz, C1), 144.5, 142.6 (t, 2JCP = 3JCF = 9 Hz, C6, C8), 140.8 (d, 2JCF = 9 Hz, C3), 133.7 (d, 1JCP = 56 Hz, C2), 127.3 (d, 1JCP = 35 Hz, C5), 116.7 (dd, 2JCF = 20, 3JCP = 8 Hz, CHc, CHd), 114.6 (dd, 2JCF = 22, 3JCP = 8 Hz, CHb), 113.1 (t, 2JCF = 3JCP = 19 Hz, CHa), 98.2 (t, 1JCRh = 2JCP = 4 Hz, C5Me5), 33.3 (dd, 1JCRh = 24, 2JCP = 7 Hz, IrCH2), 25.8 (d, 3JCP = 5 Hz, Meβ/γ), 23.4 (d, 3JCP = 7 Hz, Meβ/γ), 20.5 (Meα), 19.6 (d, 1JCP = 34 Hz, PMe), 8.5 (C5Me5). 31P{1H} NMR (160 MHz, 25 ºC, CDCl3) δ: 43.4 (d, 1JPRh = 157 Hz). 19F{1H} NMR (160 MHz, 25 ºC, CDCl3) δ: -113.0, -114.6 (d, 5JFP = 4 Hz). Rh PCl CH2 21 3 4 Meα Me 6 7 85 Meε Meγ Ha F Hb Hc F Hd Chapter III. Organometallic Rhodium Complexes with Bulky Phosphine Ligands ! ! ! ! ! ! ! 297 Complex 9e: Anal. Calc. for C28H37ClPRh: C, 61.7; H, 6.9. Found: C, ;H, . 1H NMR (500 MHz, 25 ºC, CDCl3) δ: 7.28 (d, 1 H, 3JHH = 7.5 Hz, Ha), 7.15 (m, 2 H, He, Hd/f), 7.10 (dt, 1 H, 3JHH = 7.2 Hz, 5JHP = 2 Hz, Hb), 6.87 (d, 1 H, 3JHH = 7.2, Hf/d), 6.80 (dd, 1 H, 3JHH = 7.4, 4JHP = 2.9 Hz, Hc), 3.71 (dd, 1 H, 2JHH = 13.5, 3JHP = 3.1 Hz, RhCHH), 3.43 (dd, 1 H, 2JHH = 13.4, 2JHRh = 3.4 Hz, RhCHH), 3.03 (dq, 1 H, 3JHH = 6.8, 2JHP = 21.9 Hz, PCHHCH3), 2.62 (s, 3 H, Meβ/γ), 2.36 (dq, 1 H, 3JHH = 6.9, 2JHP = 21.3 Hz, PCHHCH3), 1.96 (s, 3 H, Meα), 1.49 (s, 3 H, Meβ/γ), 1.34 (d, 15 H, 4JHP = 2.5 Hz, C5Me5), 0.72 (dt, 3 H, 3JHH = 7.3, 3JHH = 18.1 Hz, PCH2CH3). 13C{1H} NMR (125 MHz, 25 ºC, CDCl3) δ: 158.6 (d, 2JCP = 34 Hz, C1), 141.6 (d, 2JCP = 7 Hz, C4/6), 140.7 (d, 2JCP = 9 Hz, C6/4), 140.5 (C3), 134.9 (dd, 1JCP = 52, 2JCRh = 3 Hz, C2), 133.1 (d, 1JCP = 31 Hz, C5), 130.3 (d, 3JCP = 8 Hz, CHd/f), 129.7 (d, 4JCP = 2 Hz, CHb), 129.6 (d, 3JCP = 7 Hz, CHf/d), 129.2 (CHe), 126.9 (d, 3JCP = 17 Hz, CHa), 126.6 (d, 3JCP = 6 Hz, CHc), 98.9 (t, 2JCP = 1JCRh = 4 Hz, C5Me5), 33.8 (dd, 1JCRh = 25, 2JCP = 8 Hz, RhCH2), 26.1 (d, 3JCP = 5 Hz, Meβ/γ), 24.6 (d, 1JCP = 39 Hz, PCH2CH3), 24.5 (d, 3JCP = 4 Hz, Meγ/β), 20.8 (d, 3JCP = 2 Hz, Meα), 12.0 (d, 2JCP = 2 Hz, PCH2CH3), 8.8 (C5Me5). 31P{1H} NMR (200 MHz, 25 ºC, CDCl3) δ: 59.6 (d, 1JPRh = 156 Hz). Rh PCl CH2 21 3 Meα H3CH2C 5 6 4 Meε Meγ Ha Hb Hc Hd He Hf Chapter III. Organometallic Rhodium Complexes with Bulky Phosphine Ligands ! ! ! ! ! ! ! 298 Synthesis and characterization of complexes 11b-11e. To a solid mixture of complexes 9b-9e (0.08 mmol) and NaBArF (0.08 mmol), placed in a thick-wall ampoule, was added 5 mL of CH2Cl2 and the reaction mixture stirred for 10 min at room temperature under 1.5 bar of CO. After filtering, the solvent was evaporated under reduced pressure to obtain orange (11c) and yellow powders (11b, 11d, 11e) in ca. 95% yield. These complexes can be recrystallized by slow diffusion at -20 ºC of pentane into a CH2Cl2 solution (2:1 by vol.). Complex 11b: IR (Nujol): 2050 cm-1. Anal. Calc. for C62H51BF24OPRh: C, 52.7; H, 3.6. Found: C, 52.5; H, 3.7. 1H NMR (400 MHz, 25 ºC, CD2Cl2) δ: 7.20 (s, 1 H, Ha), 7.13 (s, 1 H, Hc/d), 6.94 (s, 2 H, Hd/c, Hb), 3.53 (dd, 1 H, 2JHH = 12.5, 2JHRh = 2.0 Hz, RhCHH), 3.32 (dd, 1 H, 2JHH = 12.5, 2JHRh = 4.2 Hz, RhCHH), 2.52 (s, 3 H, Meγ/ε), 2.37 (s, 3 H, Meβ/δ), 2.36 (d, 3 H, 2JHP = 9.7 Hz, PMe), 2.35 (s, 3 H, Rh PCO CH2 21 3 4 Meα Me 6 7 85 Meε Meγ Ha Meβ Hb Hc Meδ Hd BArF - Chapter III. Organometallic Rhodium Complexes with Bulky Phosphine Ligands ! ! ! ! ! ! ! 299 Meδ/β), 2.04 (s, 3 H, Meα), 1.71 (d, 15 H, 4JHP = 2.8 Hz, C5Me5), 1.53 (s, 3 H, Meε/γ). 13C{1H} NMR (100 MHz, 25 ºC, CD2Cl2) δ: 188.7 (dd, 1JCRh = 73, 2JCP = 19 Hz, CO), 152.1 (d, 2JCP = 29 Hz, C1), 142.8, 142.6 (d, 4JCP = 3 Hz, C4, C7), 142.1 (d, 1JCP = 10 Hz, C6/8), 140.3 (d, 2JCP = 8 Hz, C8/6), 139.8 (t, 2JCP = 3JCRh = 3 Hz, C3), 132.6 (dd, 1JCP = 61, 2JCRh = 3 Hz, C2), 131.8, 131.6 (d, 3JCP = 9 Hz, CHc, CHd), 130.8 (d, 3JCP = 8 Hz, CHb), 126.8 (dd, 3JCP = 17, 3JCRh = 2 Hz, CHa), 121.8 (d, 1JCP = 42 Hz, C5), 106.1 (dd, 1JCRh = 4, 2JCP = 2 Hz, C5Me5), 28.4 (d, 1JCRh = 21 Hz, RhCH2), 25.5 (d, 3JCP = 6 Hz, Meγ/ε), 25.2 (d, 1JCP = 40 Hz, PMe), 23.2 (d, 3JCP = 8 Hz, Meε/γ), 20.6 (Meβ, Meδ), 20.1 (d, 3JCP = 4 Hz, Meα), 8.6 (C5Me5). 31P{1H} NMR (160 MHz, 25 ºC, CD2Cl2) δ: 36.1 (d, 1JPRh = 126 Hz). Chapter III. Organometallic Rhodium Complexes with Bulky Phosphine Ligands ! ! ! ! ! ! ! 300 Complex 11c: IR (Nujol): 2050 cm-1. Anal. Calc. for C62H51BF24OPRh: C, 51.5; H, 3.6. Found: C, 51.4; H, 3.6. 1H NMR (500 MHz, 25 ºC, CD2Cl2) δ: 6.87 (s, 1 H, Ha), 6.82 (t, 1 H, 4JHP = 4JHH = 2.9 Hz, Hc/d), 6.67 (t, 1 H, 4JHP = 4JHH = 2.8 Hz, Hd/c), 6.64 (t, 1 H, 4JHP = 4JHH = 3.0 Hz, Hb), 3.85, 3.84 (s, 3 H, 2 OMe), 3.49 (dd, 1 H, 2JHH = 12.6, 2JHRh = 2.1 Hz, RhCHH), 3.29 (dd, 1 H, 2JHH = 12.6, 2JHRh = 4.2 Hz, RhCHH), 2.52 (s, 3 H, Meβ/γ), 2.35 (dd, 3 H, 2JHP = 9.7, 3JHRh = 1.3 Hz, PMe), 2.04 (s, 3 H, Meα), 1.72 (d, 15 H, 4JHP = 2.8 Hz, C5Me5), 1.56 (s, 3 H, Meγ/β). 13C{1H} NMR (125 MHz, 25 ºC, CD2Cl2) δ: 189.1 (dd, 1JCRh = 74, 2JCP = 19 Hz, CO), 162.9, 162.2 (d, 4JCP = 3 Hz, C4, C7), 154.7 (d, 2JCP = 31 Hz, C1), 144.8 (d, 2JCP = 11 Hz, C6/8), 143.0 (d, 2JCP = 10 Hz, C8/6), 141.7 (dd, 2JCP = 3, 3JCRh = 2 Hz, C3), 127.6 (dd, 1JCP = 65, 2JCRh = 3 Hz, C2), 116.8 (d, 3JCP = 9 Hz, CHb), 116.7 (d, 1JCP = 48 Hz, C5), 116.6 (d, 3JCP = 10 Hz, CHc, CHd), 110.8 (dd, 3JCP = 18, 3JCRh = 2 Hz, CHa), 106.4 (dd, 1JCRh = 4, 2JCP = 2 Hz, C5Me5), 55.7, 55.6 (Meδ, Meε), 28.5 (d, 1JCRh = 22 Hz, RhCH2), 26.2 (d, 3JCP = 5 Hz, Meβ/γ), 26.1 (d, 1JCP = 40 Hz, PMe), 23.8 (d, 3JCP = 8 Hz, Meγ/β), 20.7 (d, 3JCP = 3 Hz, Meα), 9.0 (C5Me5). 31P{1H} NMR (200 MHz, 25 ºC, CD2Cl2) δ: 33.8 (d, 1JPRh = 125 Hz). Rh PCO CH2 21 3 4 Meα Me 6 7 85 Meγ Meβ Ha OMe Hb Hc MeO Hd BArF - Chapter III. Organometallic Rhodium Complexes with Bulky Phosphine Ligands ! ! ! ! ! ! ! 301 Complex 11d: IR (Nujol): 2060 cm-1. Anal. Calc. for C60H45BF26OPRh: C, 50.7; H, 3.2. Found: C, 50.5; H, 3.2. 1H NMR (400 MHz, 25 ºC, CD2Cl2) δ: 7.11 (d, 1 H, 3JHF = 10.5 Hz, Ha), 7.08 (d, 1 H, 3JHF = 10.5 Hz, Hc/d), 6.90 (m, 2 H, Hb, Hd/c), 3.54 (d, 1 H, 2JHH = 12.9 Hz, RhCHH), 3.29 (dd, 1 H, 2JHH = 12.9, 3JHRh = 3.9 Hz, RhCHH), 2.57 (s, 3 H, Meβ/γ), 2.39 (d, 3 H, 2JHP = 9.5 Hz, PMe), 2.08 (s, 3 H, Meα), 1.73 (d, 15 H, 4JHP = 2.9 Hz, C5Me5), 1.60 (s, 3 H, Meγ/β). 13C{1H} NMR (100 MHz, 25 ºC, CD2Cl2) δ: 188.1 (d, 1JCRh = 73, 2JCP = 19 Hz, CO), 165.0 (dd, 1JCF = 254, 4JCP = 3 Hz, C4), 164.1 (dd, 1JCF = 255, 4JCP = 3 Hz, C7), 155.3 (dd, 2JCP = 32, 3JCF = 9 Hz, C1), 145.3 (t, 2JCP = 3JCF = 10 Hz, C6/8), 143.8 (t, 2JCP = 3JCF = 9 Hz, C8/6), 142.6 (dd, 3JCF = 9, 2JCP = 3 Hz, C3), 131.3 (d, 1JCP = 62 Hz, C2), 120.9 (d, 1JCP = 42 Hz, C5), 118.1, 117.9 (dd, 2JCF = 20, 3JCP = 10 Hz, CHc, CHd), 117.2 (dd, 2JCF = 22, 3JCP = 9 Hz, CHb), 113.2 (t, 2JCF = 3JCP = 20 Hz, CHa), 106.4 (C5Me5), 27.3 (d, 1JCRh = 21 Hz, IrCH2), 25.6 (d, 3JCP = 5 Hz, Meβ/γ), 25.2 (d, 1JCP = 40 Hz, PMe), 23.5 (d, 3JCP = 8 Hz, Meγ/β), 20.3 (Meα), 8.6 (C5Me5). 31P{1H} NMR (160 MHz, 25 ºC, CD2Cl2) δ: 34.7 (dd, 1JPRh = 128, 5JPF = 3 Hz). 19F{1H} NMR (160 MHz, 25 ºC, CD2Cl2) δ: -108.2, -110.4 (d, 5JFP = 3 Hz). Rh PCO CH2 21 3 4 Meα Me 6 7 85 Meε Meγ Ha F Hb Hc F Hd BArF - Chapter III. Organometallic Rhodium Complexes with Bulky Phosphine Ligands ! ! ! ! ! ! ! 302 Complex 11e: IR (Nujol): 2054 cm-1. Anal. Calc. for C61H49BF24OPRh: C, 52.4; H, 3.5. Found: C, 52.5; H, 3.6. 1H NMR (500 MHz, 25 ºC, CD2Cl2) δ: 7.39 (m, 3 H, 3 Har), 7.30 (m, 1 H, Har), 7.08 (m, 2 H, 2 Har), 3.65 (dd, 1 H, 2JHH = 12.9, 3JHP = 2.1 Hz, RhCHH), 3.25 (dd, 1 H, 2JHH = 12.9, 2JHRh = 4.0 Hz, RhCHH), 2.94 (m, 1 H, PCHHCH3), 2.75 (m, 1 H, PCHHCH3), 2.55 (s, 3 H, Meβ/γ), 2.00 (s, 3 H, Meα), 1.66 (d, 15 H, 4JHP = 2.8 Hz, C5Me5), 1.52 (s, 3 H, Meβ/γ), 0.65 (dt, 3 H, 3JHH = 7.5, 3JHP = 19.9 Hz, PCH2CH3). 13C{1H} NMR (125 MHz, 25 ºC, CD2Cl2) δ: 19.2 (dd, 1JCRh = 73, 2JCP = 19 Hz, CO), 153.9 (d, 2JCP = 28 Hz, C1), 142.3 (d, 2JCP = 8 Hz, C4/6), 141.4 (t, 2JCP = 4JCRh = 1 Hz, C3), 140.7 (d, 2JCP = 9 Hz, C6/4), 132.3, 132.0 (d, 4JCP = 3 Hz, CHb, CHe), 131.4, 131.0 (d, 3JCP = 9 Hz, CHd, CHf), 131.0 (dd, 1JCP = 57, 2JCRh = 3 Hz, C5), 129.3 (d, 3JCP = 7 Hz, CHc), 126.9 (dd, 3JCP = 17, 4JCRh = 2 Hz, CHa), 126.7 (d, 1JCP = 38 Hz, C2), 106.9 (bs, C5Me5), 28.6 (d, 1JCP = 34 Hz, PCH2CH3), 27.9 (dd, 1JCRh = 21, 2JCP = 2 Hz, RhCH2), 26.3 (d, 3JCP = 5 Hz, Meβ/γ), 24.4 (d, 3JCP = 7 Hz, Meγ/β), 20.4 (d, 3JCP = 3 Hz, Meα), 9.2 (d, 2JCP = 3 Hz, PCH2CH3), 8.9 (C5Me5). 31P{1H} NMR (200 MHz, 25 ºC, CD2Cl2) δ: 54.2 (d, 1JPRh = 126 Hz). Rh PCO CH2 21 3 Meα H3CH2C 5 6 4 Meε Meγ Ha Hb Hc Hd He Hf BArF - Chapter III. Organometallic Rhodium Complexes with Bulky Phosphine Ligands ! ! ! ! ! ! ! 303 Synthesis of complexes 12b-12e. To a mixture of 9b-9e (0.15 mmol) and NaBArF (0.15 mmol) was added 5 mL of CH2Cl2 under argon. The reaction mixture was stirred for 10 min at room temperature, after which the solution turned from orange to red. The resulting suspension was filtered and the solvent evaporated under reduced pressure to obtain compounds 12b-12e as red solids in ca. 95% yield. For further purification, the complexes can be recrystallized by slow diffusion at -20 ºC of pentane into a CH2Cl2 solution (2:1 by vol.). Compound 12b: Anal. Calc. for C61H51BF24PRh: C, 52.9; H, 3.7. Found: C, 52.6; H, 3.7. 1H NMR (400 MHz, 25 ºC, CDCl3) δ: 7.34 (s, 1 H, Hb), 6.88, 6.76 (s, 1 H, Hc/d), 6.60 (s, 1 H, Ha), 2.91 (dt, 1 H, 2JHH = 4.0, 2JHRh = 3JHP = 1.3 Hz, RhCHα), 2.51 (s, 3 H, Meγ/ε), 2.44 (s, 3 H, Meα), 2.36 (s, 3 H, Meβ), 2.20 (s, 3 H, Meδ), 2.11 (d, 3 H, 2JHP = 13.0 Hz, PMe), 1.97 (s, 3 H, Meε/γ), 1.61 (d, 15 H, 4JHP = 2.7 Hz, C5Me5), 1.29 (ddd, 1 H, 3JHP = 13.9, 2JHH = 4.0, 2JHRh = 0.7 Hz, RhCHβ). 34 1 2 Meα P Rh Me 8 5 6 7 Hd MeδHcHb Meβ Ha Hβ Hα Meγ Meε BArF - Chapter III. Organometallic Rhodium Complexes with Bulky Phosphine Ligands ! ! ! ! ! ! ! 304 13C{1H} NMR (100 MHz, 25 ºC, CDCl3) δ: 144.1 (C4), 143.2 (C8), 141.9, 140.9 (C5, C7), 137.3 (C3), 134.7 (CHb), 130.4, 130.3 (CHc, CHd), 125.1 (d, 3JCP = 8 Hz, CHa), 116.7 (d, 1JCP = 58 Hz, C6), 104.6 (dd, 1JCRh = 14, 2JCP = 4 Hz, C1), 98.8 (dd, 1JCRh = 6, 2JCP = 2 Hz, C5Me5), 74.4 (d, 1JCP = 25 Hz, C2), 41.5 (dd, 2JCP = 15, 1JCRh = 2 Hz, RhCH2), 22.5 (Meα), 21.7, 21.5 (Meγ/ε), 21.1 (Meβ), 20.9 (Meδ), 13.0 (d, 1JCP = 33 Hz, PMe), 8.9 (C5Me5). 31P{1H} NMR (160 MHz, 25 ºC, CDCl3) δ: - 15.7 (d, 1JPRh = 138 Hz). Chapter III. Organometallic Rhodium Complexes with Bulky Phosphine Ligands ! ! ! ! ! ! ! 311 J. López-Serrano, L. Sánchez, F. P. Cossio, A. de Cozar, E. Álvarez, C. Maya, E. Carmona, J. Am. Chem. Soc. 2010, 132, 16765–16767. [31] a) J. Atzrodt, V. Derdau, T. Fey, J. Zimmermann, Angew. Chem. Int. Ed. 2007, 46, 7744-7765; b) N. Elander, J. R. Jones, S.-Y. Lu, S. Stone-Elander, Chem. Soc. Rev. 2000, 29, 239-249. [32] A. R. O’Connor, W. Kaminsky, B. C. Chan, D. M. Heinekey, K. I. Goldberg, Organometallics 2013, 32, 4016-4019. [33] a) S. Michlik, R. Kempe, Nature Chem. 2013, 5, 140-144; b) J. Graeupner, T. P. Brewster, J. D. Blakemore, N. D. Schley, J. M. Thomsen, G. W. Brudvig, N. Hazari, R. H. Crabtree, Organometallics 2012, 31, 7158-7164; c) M. Prinz, L. F. Veiros, M. J. Calhorda, C. C. Romão, E. Herdtweck, F. E. Kühn, W. A. Herrmann, J. Organomet. Chem. 2006, 691, 4446–4458; d) C. G. Pierpont, Inorg. Chem. 1979, 18, 2972–2977. [34] A. Zamorano, N. Rendón, J. E. Valpuesta, E. Álvarez, E. Carmona, Inorg. Chem. 2015, 54, 6573-6581. [35] See for instance: a) R. Uson, L. A. Oro, C. Foces-Foces, F. H. Cano, S. García-Blanco, M. Valderrama, J. Organomet. Chem. 1982, 229, 293-304 ; b) R. Uson, L. A. Oro, C. Foces-Foces, F. H. Cano, A. Vegas, M. Valderrama, J. Organomet. Chem. 1981, 215, 241–253. [36] a) J. Campos, M. Rubio, A. C. Esqueda, E. Carmona, J. Labelled Compd. Radiopharm. 2012, 55, 29-38; b) J. Campos, A. C. Esqueda, E. Carmona, P201000507, España, 2010. [37] a) N. A. Yakelis, R. G. Bergman, Organometallics 2005, 24, 3579-3581; b) R. Bloom, J. Boersma, P. H. M. Budzelaar, B. Fischer, A. Haaland, H. V. Volden, J. Weidlein, Acta Chem. Scand. 1986, 40, 113-120; c) G. Giordano, R. H. Crabtree, Inorg. Synth. 1979, 19, 218-220; d) R. Cramer, Inorg. Synth. 1974, 14, 15. ! 312 CONCLUSIONES 1. Se ha procedido a la síntesis y la caracterización estructural de los alquilos de Au(I), [Au(R)(PMe2Ar’)], para R = Me, Et y CH2CMe2Ph, en los que el ligando estabilizador es la fosfina voluminosa PMe2Ar’, que contiene un sustituyente terfenilo, Ar’ = C6H3-2,6-(C6H3-2,6- Pri2)2. Estos complejos interaccionan con el fragmento catiónico [Au(PMeAr’)]+, generando in situ en disolución, de manera espontánea, a partir del complejo de triflimidato [Au(NTf2)(PMe2Ar’)], para formar los primeros alquilos catiónicos binucleares de oro que se describen en la bibliografía, los cuales poseen un ligando alquilo que sirve de puente entre dos átomos de Au(I). Aunque estos complejos poseen una estabilidad térmica relativamente baja, el derivado de metilo [Au2(µ- Me)(PMe2Ar’)][NTf2] se ha caracterizado de forma completa, tanto en disolución como en estado sólido y presenta una coordinación simétrica Au-Me-Au. 2. El mismo método de síntesis ha hecho posible el aislamiento de complejos análogos [Au(µ-R)(PMe2Ar’)2][NTf2] en los que R es vinilo (-CH=CH2) o acetiluro (-C≡CH), complejos de gran interés puesto que sirven de modelo para los intermedios que se postulan de forma generalizada en numerosas transformaciones de alquenos, alquinos, alenos, etc., catalizadas en fase homogénea por complejos de Au(I). En disolución, estos compuestos tienen un comportamiento dinámico que se traduce en la equivalencia de los fragmentos Au(PMe2Ar’), 313 pero en el estado sólido la coordinación no es simétrica, sino que uno de los átomos de oro se enlaza al grupo etenilo o etinilo mediante un enlace covalente normal de 2c-2e, y el otro mediante uno covalente donador (o covalente dativo), en el que recibe densidad electrónica de un enlace π del fragmento orgánico insaturado. Los complejos binucleares con un grupo R puente Me, -CH=CH2 o -C≡CH, presentan una interacción aurofílica que varía en el orden Me > -CH=CH2 > - C≡CH, según permiten concluir los estudios de difracción de rayos X efectuados. 3. El complejo catiónico [(ƞ5-C5Me5)Ir(C^P)(CH2Cl2)]+, 2·CH2Cl2, reacciona inicialmente con los alquinos HC≡CH, PhC≡CMe y PhC≡CH formado los correspondientes aductos, 2·alquino, en los que la molécula del hidrocarburo se une al átomo de Ir(III) mediante la coordinación π habitual. Los tres complejos tienen, sin embargo, diferente reactividad y, al menos los de PhC≡CH y PhC≡CMe, evolucionan mediante mecanismos diferentes que conducen a productos finales de naturaleza asimismo diversa. En los tres sistemas estudiados se observaron reacciones de activación de enlaces C—H y de formación de enlaces C—C que condujeron a un grupo funcional de tipo alqueno o alilo como parte constituyente de un ligando de naturaleza compleja y elaborada que deriva de la fosfina metalada del complejo precursor. Los estudios isotópicos realizados con el hidrocarburo deuterado PhC≡CD demostraron su tautomería inducida por el complejo Ir(III) al correspondiente vinilideno Ir=C=C(D)Ph+, como etapa previa a la formación de un nuevo enlace C—C. El sistema de PhC≡CMe evolucionó, en cambio, mediante un mecanismo 314 de inserción migratoria, mientras que para el complejo de HC≡CH no fue posible discriminar entre ambos caminos de reacción. 4. Mediante un fragmento TpMe2Ir(III), isoelectrónico con el (C5Me5)Ir(III) del apartado anterior, se ha conseguido estabilizar un metalaciclo que contiene un ligando orgánico bidentado de naturaleza alquilideno-alquilo, a saber, Ir=CH-C(Me)=C(Me)-CH2, el cual presenta una estabilidad inusual para un complejo catiónico de esta clase. Al mismo tiempo tiene una reactividad singular que se manifiesta en la acidez de Brönsted-Lowry de algunos de sus enlaces C—H, en su capacidad para isomerizarse a una estructura abierta de butadienilo, Ir-CH2=C(Me)-C(Me)=CH2, y sobre todo en su tendencia a experimentar reacciones de acoplamiento C—C con dos moléculas de acetonitrilo. Esta transformación es catalizada por agua y origina un complejo metalabicíclico con una estructura estéticamente muy atractiva que se asemeja a la del hidrocarburo insaturado e igualmente bicíclico conocido como barreleno. 5. El estudio de la reactividad del complejo [Rh(µ-Cl)(COD)]2 frente a fosfinas de terfenilo PMe2Ar’, para Ar’ = ArXyl2 y ArDipp2, ha puesto de manifiesto la versatilidad de la coordinación de estos ligandos que pueden comportarse como mono o polidentados. Si existe sólo una posición de coordinación accesible se produce la coordinación monodentada clásica, κ , P, en la que la fosfina actúa como donador de dos electrones, como se ha demostrado para los complejos de composición [RhCl(η2-COD)(PMe2Ar’)] y [RhCl(CO)2(PMe2Ar’)]. Pero si en estos últimos se elimina el ligando cloruro (por acción de 315 NaBArF), se induce de forma instantánea una reorganización que lleva a la coordinación quelatante κ , P, η2-areno en la que la fosfina se comporta como ligando tetradentado donador de (2+6) electrones, gracias a la participación en el enlace de uno de los grupos arilo latentes del grupo terfenilo. Estos cambios se han probado de forma inequívoca en algunos de los sistemas investigados y explican además la compleja reactividad que se manifiesta cuando los carbonilos catiónicos [Rh(CO)n(PMe2ArXyl2)]+ se generan bajo una presión de CO de 6 bar. 6. Los compuestos metalacíclicos 12, que contienen la agrupación (η5- C5Me5)Rh(III) y resultan de la ciclometalción de fosfinas de tipo PR(Xyl’)2, representando Xyl’ a un grupo 2,6-Me2C6H2-4-R’, con el sustituyente R’ = Me, OMe y F, tienen una reactividad química muy similar a la encontrada inicialmente para el complejo análogo en el que R’ = H. Puede concluirse que el sustituyente en la posición para tiene poca influencia en la capacidad donadora global de la fosfina, conclusión avalada por los valores análogos de ν(CO) encontrados para los carbonilos cationes 9 al variar R’ (Me, OMe y F, comparados además con R’ = H), y también por el comportamiento semejante que exhiben todos los complejos frente a la molécula de H2. La actividad catalítica de los complejos 12 frente a los intercambios Si-H/Si-D en hidrosilanos y respecto a la hidrosililación de cetonas aromáticas es asimismo poco sensible a la naturaleza del sustituyente R’. !