Reactivity of Schiff base-[C,N,S] pincer palladacycles: hydrolysis renders singular trinuclear, tetranuclear, and heteropentanuclear Pd3W2 coordinated complexes

Dalton Transactions An international journal of inorganic chemistry rsc.li/dalton ISSN 1477-9226 Volume 53 Number 23 21 June 2024 Pages 9599-10022 PAPER José M. Vila et al. Reactivity of Schiff base-[C,N,S] pincer palladacycles: hydrolysis renders singular trinuclear, tetranuclear, and heteropentanuclear Pd 3 W 2 coordinated complexes Dalton Transactions PAPER Cite this: Dalton Trans., 2024, 53, 9680 Received 13th March 2024, Accepted 12th April 2024 DOI: 10.1039/d4dt00756e rsc.li/dalton Reactivity of Schiffbase-[C,N,S] pincer palladacycles: hydrolysis renders singular trinuclear, tetranuclear, and heteropentanuclear Pd 3 W 2 coordinated complexes† Francisco Reigosa, ‡Paula M. Polo,‡M. Teresa Pereira and José M. Vila * Treatment of the Schiffbase ligands a–fwith Li 2 [PdCl 4 ]/NaAcO in methanol under reflux gave the single nuclear palladacycles 1a–1f, with the metal atom bonded to a terdentate monoanionic [C,N,S] iminic ligand and to a chloride ligand that completes the palladium coordination sphere. Reaction of 1a–1c with silver perchlorate/triphenylphosphine in acetone at room temperature yielded the single nuclear complexes 2a–2c as the perchlorate salts, after substitution of the chloride ligand by a triphenylphosphine. However, reaction of a–cwith Na 2 [PdCl 4 ]/NaAcO in methanol at room temperature also gave compounds 1a–1c albeit contaminated with small amounts of the corresponding free aldehyde (mixture A). Reaction of mixture A with silver perchlorate/triphenylphosphine in acetone at room temperature gave analogously 2a–2c with some of the corresponding free aldehyde (mixture B). Attempts to purify mixtures A and B via recrystallization produced single crystals of 5and 6respectively: two serendipitously formed complexes, bearing thiomethyl aniline and/or acetate ligands, and void of aldehyde or iminic residue; the structures contain eight- and six-membered rings of alternating palladium and nitrogen atoms, respectively. To clarify this situation the aniline itself was reacted with palladium(II) acetate or with Na 2 [PdCl 4 ]; in the latter case after recrystallization a unique behavior is revealed, giving rise to a tetranuclear complex containing a Pd 4 N 4 ring with three differing coordination environments on the palladium atoms. Treatment of 1d with Ph 2 PCH 2 PPh 2 (dppm)/AgClO 4 or with Ph 2 PCH 2 (PPh 2 )W(CO) 5 /AgClO 4 gave 3d, with a mono-coordinated dppm ligand, and 4d, respectively; complex 3d could not be converted into 4d by reaction with W(CO) 5 (THF). Recrystallization of 4d gave a still further noticeable species, complex 8:a pentanuclear trans-configured heterometallic mixed valent Pd(II)/W(0) linear complex with the palladium atoms supported by two acetate and two thiomethyl aniline bridging ligands. The complexes were fully characterized by microanalysis, IR, 1 H, and 31 P NMR spectroscopies, as appropriate. The X-ray singlecrystal analyses for compounds 1b,5,6,7and 8are described. Introduction The chemistry of palladacycles, 1,2 first reported by Cope and Siekman, 3 constitutes a flourishing part of organometallics that has attracted much research interest in past years attributable to a great extent to their versatile structural and reactivity features, mainly derived from the fact that their properties can be easily tuned, for example by modification of the cyclometallated ligand or the ancillary ligands at the metal. They are also well known for their broad applications 4 in numerous fields such as in organic synthesis, 5,6 photochemistry, 7,8 optical resolution processes, 9 and catalysis, which after the pioneering work by Herrmann et al., 10,11 continues to be researched, 12–21 as potential biologically active materials, 22–31 and liquid crystals. 32–34 In the past we have shown that thiosemicarbazones yield palladacycles with the ligand in a terdentate [C,N,S] fashion 35 with formation of tetranuclear compounds possessing two distinct palladium–sulfur bonds, i.e.,Pd–S chelating and Pd–S bridging , with the ligand in a pincer mode; Kawamoto et al. 36 have reported similar structures for Schiffbase [C,N,S] Pd(II)and Pt(II) complexes. This results in three strong bonds at the metal, namely the Pd–C, Pd–NandPd–S chelating bonds pertaining to two fused five-membered rings, that maintain the metal tightly bonded so that only one of the four coordination sites in the †CCDC 2333528 (1b), 2333529 (5), 2333530 (7), 2333531 (6) and 2333532 (8). For crystallographic data in CIF or other electronic format see DOI: https://doi.org/ 10.1039/d4dt00756e ‡Both authors contributed equally. Departamento de Química Inorgánica, Universidad de Santiago de Compostela, E-15782 Santiago de Compostela, Spain. E-mail: josem[email protected] 9680 |Dalton Trans.,2024,53, 9680–9691 This journal is © The Royal Society of Chemistry 2024 Open Access Article. Published on 19 April 2024. Downloaded on 7/10/2024 7:49:16 AM. This article is licensed under a Creative Commons Attribution-NonCommercial 3.0 Unported Licence. View Article Online View Journal | View Issue square-planar palladium environment is capable of further reaction. Earlier results by this laboratory also put forward that the said complexes react with small bite strong chelating diphosphines to give species with an uncoordinated phosphorus donor atom, 37 thus performing as metalloligands, which were able to coordinate to a second metal atom, providing homo- and heterobimetallics. We then sought out to look for analogous systems that would retain the excellent pincer properties of the terdentate [C,N,S] ligands and for this purpose Schiffbases derived from 2-thiomethylaniline were chosen; this changes the thiosemicarbazone sequence –C(Me)vN–N(H)–C(NHR)–Sto the corresponding Schiffbase one –C(H)vN–CvC–SMe. We reasoned that these related systems bearing analogous backbones of nitrogen and sulfur donors would behave likewise and even in the absence of the thiolate sulfur the non-thiolate thiomethyl group would bind well in agreement with Pearson’s concept. 38 The preparation of [C,N,S] metallacycles can be achieved by quite numerous routes such as reactions with lithium derivatives, 39 oxidative addition and photooxidation, 40 and direct orthometallation for which Pd(DMSO) 2 Cl 2 , 41 Pd(OAc) 2 , Li 2 [PdCl 4 ]orNa 2 [PdCl 4 ] are amongst the more common reagents. The lithium salt has proven to be a quite useful palladium source for the synthesis of palladacycles, and was used in the present preparations, albeit requires prior synthesis of the salt using moisture-sensitive reagents; therefore, the commercially available sodium salt was also used to compare results and to reduce the synthetic steps. Thus, the latter two were chosen and although the initial steps seemed to agree with the expectations the ensuing iminic metalloligands and the corresponding bimetallics similar to those mentioned above, could not be prepared from the sodium salt, drifting the process to a different route: we tentatively attribute this to partial hydrolysis of the iminic ligand. The spontaneous decay of the products yielded unprecedented rearrangements producing tri- and tetranuclear homometallic complexes, with the methylthioaniline precursor simultaneously acting as a chelating and bridging ligand, leading to new insights into their chemistry. This led us to study the reactivity of the 2-thiomethylaniline itself to test our hypothesis. Furthermore, the bimetallic palladium/tungsten also decayed on recrystallization to yield a pentanuclear heterometallic complex. A more recent example related to spontaneous palladacycle disruption has been reported by us related to the Schiffbase palladacycles: an innovate structural rearrangement from single-nuclear to double-nuclear pseudo-penta- coordinated complexes, that we dare say is even more surprising since it could be termed as a special case of selfcyclopalladation. 42 We tentatively coin these processes as typical cases of serendipity in palladacycle chemistry, which on the other hand put forward novel and exciting reactivity patterns yet to be accounted for, developing new substances that may be of use in any of the fields of application of these compounds. In this work we report palladacycles bearing tridentate [C,N,S] Schiffbase ligands and differing palladium salts, together with the corresponding reactions with mono- and diphosphines, leading to the discovery of new multinuclear complexes. Experimental section General procedures Solvents were purified by standard methods. Chemicals (lithium chloride, palladium(II) chloride), the phosphines PPh 3 and Ph 2 PCH 2 PPh 2 (dppm), aldehydes and 2-thiomethyl aniline were used as supplied from commercial sources. Lithium tetrachloropalladate was made in situ by treating palladium(II) chloride with lithium chloride in methanol. Ph 2 PCH 2 P(Ph 2 )W (CO) 5 was prepared by literature synthesis. Microanalyses were carried out at the Servicio de Análisis Elemental at the University of Santiago using a FISONS elemental analyzer, Model 1108. IR spectra were recorded as KBr pellets or polythene discs on BRUKER Model IFS-66v and IR-FT Mattson Model Cygnus-100 spectrophotometers, and on a JASCO FT/ IR-4600 spectrometer equipped with an ATR, model ATR-PRO ONE. NMR spectra were obtained as CDCl 3 , DMSO-d 6 or Me 2 CO-d 6 solutions as appropriate and referenced to SiMe 4 ( 1 H) or 85% H 3 PO 4 ( 31 P–{ 1 H}) and were recorded on BRUKER DPX 250 and Varian Inova 400 spectrometers. All chemical shifts, in ppm, were reported downfield from the standards. Syntheses Preparation of the ligands The corresponding aldehyde and 2-thiomethyl aniline were added together in chloroform (ca.30cm 3 ) in a round-bot- tomed flask to give a pale-yellow solution which was refluxed in a modified Dean–Stark apparatus under dry nitrogen for 24 h, after which the resulting yellow to dark-yellow solution was cooled to room temperature and the solvent removed under reduced pressure. 3,4-(OMe) 2 C 6 H 3 C(H)vN[2-(SMe)C 6 H 4 ]a.Yellow solid. Yield: 87%. 1 H NMR (400 MHz, DMSO-d 6 )δ8.40 (s, 1H, HCvN), 7.66 (s, 1H, H2), 7.47 (dd, 3 J= 8.3 Hz, 4 J= 1.9 Hz, 1H, H6), 7.24 (td, 3 J= 7.3 Hz, 4 J= 1.7 Hz, 1H, H10), 7.19 (d, 3 J= 7.3 Hz, 1H. H11), 7.15 (td, 3 J= 7.3 Hz, 4 J= 1.7 Hz, 1H, H9), 7.08 (dd, 3 J= 8.3 Hz, 4 J= 2.0 Hz, 1H, H5), 7.04 (dd, 3 J= 7.6 Hz, 4 J= 1.7 Hz, 1H, H8), 3.89 (s, 6H, OMe), 2.42 (s, 3H, SMe). IR cm −1 ν(CvN) 1618. Anal. found: C, 67.1; H, 5.9; N, 5.0; S, 10.9%, C 16 H 17 NO 2 S (287.38 g mol −1 ) requires C, 66.9; H, 6.0; N, 4.9; S, 11.2%. 3-Me-4-OMeC 6 H 3 C(H)vN[2-(SMe)C 6 H 4 ]b.Yellow solid. Yield: 92%. 1 H NMR (400 MHz, DMSO-d 6 )δ8.39 (s, 1H, HCvN), 7.82 (d, 4 J= 2.1 Hz, 1H, H2), 7.77 (dd, 3 J= 8.4 Hz, 4 J= 2.3 Hz, 1H, H6), 7.23 (td, 3 J= 7.4 Hz, 4 J= 1.7 Hz, 1H, H10), 7.18 (dd, 3 J= 7.7 Hz, 4 J= 1.7 Hz, 1H, H11), 7.15 (td, 3 J= 7.4 Hz, 4 J= 1.8 Hz, 1H), 7.06 (d, 3 J= 8.4 Hz, 1H, H5), 7.03 (dd, 3 J= 7.5 Hz, 4 J= 1.6 Hz, 1H, H8), 3.93 (s, 3H, OMe), 2.42 (s, 3H, SMe), 2.25 (s, 3H, Me). IR cm −1 ν(CvN) 1625. Anal. found: C, 70.5; H, 6.2; N, 5.2; S, 11.9%, C 16 H 17 NOS (271.38 g mol −1 ) requires C, 70.8; H, 6.3; N, 5.2; S, 11.8%. Dalton Transactions Paper This journal is © The Royal Society of Chemistry 2024 Dalton Trans.,2024,53, 9680–9691 | 9681 Open Access Article. Published on 19 April 2024. Downloaded on 7/10/2024 7:49:16 AM. This article is licensed under a Creative Commons Attribution-NonCommercial 3.0 Unported Licence. View Article Online 3,4-(OCH 2 CH 2 O)C 6 H 3 C(H)vN[2-(SMe)C 6 H 4 ]c.Orange oil. Yield: 88%. 1 H NMR (400 MHz, acetone-d 6 )δ8.38 (s, 1H, HCvN), 7.52 (s, 1H, H2), 7.46 (d, 3 J= 8.7 Hz, 1H, H6), 7.23 (m, 2H, H9/H11), 7.18–7.13 (m, 1H), 7.04 (d, 3 J= 8.2 Hz, 1H, H8), 6.96 (d, 3 J= 8.3 Hz, 1H, H5), 4.34 (d, 3 J= 5.4 Hz, 4H, CH 2 ), 2.42 (s, 3H, SMe). IR cm −1 ν(CvN) 1621. Anal. found: C, 67.1; H, 5.3; N, 4.7; S, 11.5%, C 16 H 15 NO 2 S (285.36 g mol −1 ) requires C, 67.3; H, 5.3; N, 4.9; S, 11.2%. 4-OMeC 6 H 4 C(H)vN[2-(SMe)C 6 H 4 ]d.Yellow oil. Yield 85%. 1 H NMR (250 MHz, DMSO-d 6 )δ8.44 (s, 1H, HCvN), 7.88 (vd, N= 8.0 Hz, 2H, H2, H6), 7.10–7.30 (m, 4H, H9, H10, H11, H12), 7.07 (vd, N= 8.0 Hz, 2H, H3, H5), 3.82 (s, 3H, OMe), 2.37 (s, 3H, SMe). IR cm −1 ν(CvN) 1626. Anal. found: C, 70.1; H, 6.0; N, 5.7; S, 12.3%, C 15 H 15 NOS (257.35 g mol −1 ) requires C, 70.0; H, 5.9; N, 5.4; S, 12.5%. 2,4-(OMe) 2 C 6 H 4 C(H)vN[2-(SMe)C 6 H 4 ]e.Yellow oil. Yield 82%. 1 H NMR (250 MHz, CDCl 3 )δ8.73 (s, 1H, HCvN), 8.19 (d, 3 J(H6H5) = 8.7 Hz, 1H, H6), 6.93–7.17 (m, 4H, H9, H10, H11, H12), 6.56 (dd, 3 J(H5H6) = 8.7 Hz, 4 J(H5H3) = 2.3 Hz, 1H, H5), 6.43 (d, 4 J(H3H5) = 2.3 Hz, 1H, H3), 3.84 (s, 3H, OMe), 3.82 (s, 3H, OMe), 2.42 (s, 3H, SMe). IR cm −1 ν(CvN) 1601. Anal. found: C, 67.0; H, 5.9; N, 5.0; S, 11.0%, C 16 H 17 NO 2 S (287.38 g mol −1 ) requires C, 66.8; H, 6.0; N, 4.9; S, 11.2%. 2,3,4-(OMe) 3 C 6 H 4 C(H)vN[2-(SMe)C 6 H 4 ]f.Yellow oil. Yield 98%. 1 H NMR (250 MHz, CDCl 3 ): δ8.65 (s, 1H, HCvN), 7.97 (d, 3 J(H6H5) = 8.8 Hz, 1H, H6), 6.70–7.18 (m, 4H, H9, H10, H11, H12), 6.96 (d, 3 J(H5H6) = 8.8 Hz, 1H, H5), 3.94 (s, 3H, OMe), 3.90 (s, 3H, OMe), 3.87 (s, 3H, OMe), 2.43 (s, 3H, SMe). IR cm −1 ν(CvN) 1623. Anal. found: C, 64.1; H, 6.0; N, 4.5; S, 10.2%, C 17 H 19 NO 3 S (317.40 g mol −1 ) requires C, 64.3; H, 6.0; N, 4.4; S, 10.1%. Preparation of the chloride compounds Route a: Palladium chloride and lithium chloride were added together in oxygen-free methanol in a carousel flask under argon. The mixture was stirred at room temperature until a reddish color appeared. Then, the ligand was added and a color change was observed, followed by turbidity and by the formation of a solid within the solution. The reaction mixture was heated to 70 °C for 4 h and one equivalent of sodium acetate was added, which produced the instantaneous formation of an orange solid that was separated by centrifugation. Route b: In a 100 mL round bottom flask the ligand was dissolved in methanol with stirring and at room temperature. Then, sodium tetrachloropalladate was added, followed by sodium acetate, and upon further stirring the formation of an orange precipitate was observed. The solid was separated by filtration, washed and dried under vacuum. Route c (for 1d,1e,1f): To a stirred dark-red solution of lithium tetrachloropalladate(II) in methanol the ligand, d,e,f, was added and the mixture was refluxed for 1 h under dry dinitrogen. After cooling to room temperature sodium acetate was added to the resulting solution. The solid formed was filtered off, washed with ethanol and air-dried. [Pd{3,4-(OMe) 2 C 6 H 2 C(H)vN[2-(SMe)C 6 H 4 ]}(Cl)] 1a. Orange solid. Yield: 58%. 1 H NMR (400 MHz, CDCl 3 )δ8.51 (s, 1H, HCvN), 7.60 (d, 3 J= 8.0 Hz, 1H, H11), 7.57 (t, 3 J= 8.0 Hz, 1H, H10), 7.46 (s, 1H, H2), 7.45 (td, 3 J=8.4Hz, 4 J= 1.4 Hz, 1H, H9), 7.40–7.33 (m, 1H), 7.02 (s, 1H, H5), 4.01 (s, 3H, OMe), 3.86 (s, 3H, OMe), 2.81 (s, 3H, SMe). IR cm −1 ν(CvN) 1579; ν(Pd–Cl) 322. Anal. found: C, 45.1; H, 3.8; N, 3.5; S, 7.3%, C 16 H 16 ClNO 2 PdS (428.24 g mol −1 ) requires C, 44.9; H, 3.8; N, 3.3; S, 7.5%. [Pd{3-Me-4-OMeC 6 H 2 C(H)vN[2-(SMe)C 6 H 4 ]}(Cl)] 1b. Orange solid. Yield: 63%. 1 H NMR (400 MHz, CDCl 3 )δ8.47 (s, 1H, HCvN), 7.60 (dd, 3 J= 8.5 Hz, 4 J= 1.2 Hz, 1H), 7.57 (dd, 3 J= 7.8 Hz, 4 J= 1.5 Hz, 1H), 7.44 (td, 3 J= 8.4 Hz, 4 J= 1.5 Hz, 1H), 7.39 (s, 1H, H2), 7.38–7.29 (m, 2H), 3.96 (s, 3H, OMe), 2.81 (s, 3H, SMe), 2.14 (s, 3H, Me). IR cm −1 ν(CvN) 1581; ν(Pd–Cl) 329. Anal. found: C, 46.7; H, 3.9; N, 3.6; S, 7.9%, C 16 H 16 ClNOPdS (412.24 g mol −1 ) requires C, 46.6; H, 3.9; N, 3.4; S, 7.8%. [Pd{3,4-(OCH 2 CH 2 O)C 6 H 2 C(H)vN[2-(SMe)C 6 H 4 ]}(Cl)] 1c. Orange solid. Yield: 74%. 1 H NMR (400 MHz, acetone-d 6 )δ 9.01 (s, 1H, HCvN), 7.99 (d, 3 J= 8.4 Hz, 1H, H11), 7.81 (d, 3 J= 7.8 Hz, 1H, H8), 7.58 (t, 3 J= 7.4 Hz, 3H, H10), 7.48 (t, 3 J= 8.0 Hz, 1H, H9), 7.21 (s, 1H, H2), 7.14 (s, 1H, H5), 7.34 (d, J= 4.1 Hz, 2H, CH 2 ), 4.27 (s, 2H, CH 2 ), 2.82 (d, J= 1.6 Hz, 3H, SMe). IR cm −1 ν(CvN) 1581; ν(Pd–Cl) 327. Anal. found: C, 44.8; H, 3.2; N, 3.1; S, 7.2%, C 16 H 14 ClNO 2 PdS (426.22 g mol −1 ) requires C, 45.1; H, 3.3; N, 3.3; S, 7.5%. [Pd{4-OMeC 6 H 3 C(H)vN[2-(SMe)C 6 H 4 ]}(Cl)] 1d. Yellow solid. Yield 83%. 1 H NMR (250 MHz, DMSO-d 6 ): δ9.12 (s, 1H, HCvN), 7.98 (d, 3 J(H11H12) = 8.4 Hz, 1H, H12), 7.83 (d, 3 J(H9H10) = 7.9 Hz, 1H, H9), 7.55 (t, 3 J(H10H11) = 8.0 Hz, 1H, H10), 7.53 (d, 3 J(H2H3) = 8.8 Hz, 1H, H2), 7.44 (t, 1H, H11), 7.11 (d, 4 J(H5H3) = 2.7 Hz, 1H, H5), 6.71 (dd, 1H, H3), 3.80 (s, 3H, OCH 3 ), 2.75 (s, 3H, SCH 3 ). IR 1603 ν(CvN), 315 ν(Pd–Cl trans-N )cm −1 . Anal. found: C, 45.0; H, 3.4; N, 3.4; S, 8.0%, C 15 H 14 ClNOPdS (398.22 g mol −1 ) requires C, 45.2; H, 3.5; N, 3.5; S, 8.1%. [Pd{2,4-(OMe) 2 C 6 H 3 C(H)vN[2-(SMe)C 6 H 4 ]}(Cl)] 1e. Orange solid. Yield 77%. 1 H NMR (250 MHz, CDCl 3 )δ8.77 (s, 1H, HCvN), 7.61 (d, 3 J(H11H12) = 8.2 Hz, 1H, H12), 7.51 (d, 3 J(H9H10) = 7.8 Hz, 1H, H9), 7.39 (t, 1H, H10), 7.27 (t, 1H, H11), 7.03 (d, 4 J(H5H3) = 2.1 Hz, 1H, H5), 6.06 (d, 4 J(H3H5) = 2.1 Hz, 1H, H3), 3.89 (s, 3H, OMe), 3.80 (s, 3H, OMe), 2.77 (s, 3H, SMe). IR 1585 ν(CvN), 332 ν(Pd–Cl trans-N )cm −1 . Anal. found: C, 45.1; H, 3.8; N, 3.2; S, 7.4%, C 16 H 16 ClNO 2 PdS (428.24 g mol −1 ) requires C, 44.9; H, 3.8; N, 3.3; S, 7.5%. [Pd{2,3,4-(OMe) 3 C 6 H 3 C(H)vN[2-(SMe)C 6 H 4 ]}(Cl)] 1f. Yellow solid. Yield 82%. 1 H NMR (250 MHz, CDCl 3 )δ8.73 (s, 1H, HCvN), 7.64 (d, 3 J(H12H11) = 8.3 Hz, 1H, H12), 7.54 (d, 3 J(H9H10) = 7.7 Hz, 1H, H9), 7.42 (t, 3 J(H10H11) = 7.2 Hz, 1H, H10), 7.15 (s, 1H, H5); 7.30 (t, 1H, H11), 4.02 (s, 3H, OMe), 3.95 (s, 3H, OMe), 3.77 (s, 3H, OMe), 2.76 (s, 3H, SMe). IR 1606 ν(CvN), 333 ν(Pd–Cl trans-N )cm −1 . Anal. found: C, 44.5; H, 3.9; N, 3.2; S, 7.1%, C 17 H 18 ClNO 3 PdS (458.27 g mol −1 ) requires C, 44.6; H, 4.0; N, 3.1; S, 7.0%. Preparation of the triphenylphosphine palladacycles The appropriate palladacycle and silver perchlorate were added in acetone (15 mL) in a carousel tube to give a light orange Paper Dalton Transactions 9682 |Dalton Trans.,2024,53, 9680–9691 This journal is © The Royal Society of Chemistry 2024 Open Access Article. Published on 19 April 2024. Downloaded on 7/10/2024 7:49:16 AM. This article is licensed under a Creative Commons Attribution-NonCommercial 3.0 Unported Licence. View Article Online solution, which was stirred for 10 min. Then, the solution becomes dark orange and the resulting white solid (AgCl) was removed by centrifugation prior to addition of triphenylphosphine. Removal of the solvent under reduced pressure gave the expected complex as an orange solid, which was filtered offand dried. [Pd{3,4-(OMe) 2 C 6 H 2 C(H)vN[2-(SMe)C 6 H 4 ]}(PPh 3 )][ClO 4 ] 2a. Orange solid. Yield: 78%. 1 H NMR (400 MHz, acetone-d 6 )δ 9.29 (d, 4 J P–H = 9.3 Hz, 1H, HCvN), 8.05 (d, 3 J= 8.4 Hz, 1H, H11), 7.89–7.81 (m, 7H), 7.74–7.51 (m, 9H), 7.43 (s, 1H, H2), 6.83 (t, 3 J= 7.8 Hz, 1H, H9), 6.61 (t, 3 J= 7.8 Hz, 1H, H10), 6.05 (d, 4 J P–H = 5.3 Hz, 1H, H5), 3.76 (s, 3H, OMe), 2.93 (s, 3H, OMe), 2.12 (s, 3H, SMe). 31 P-NMR (400 MHz, acetone-d 6 )δ 38.89. IR ν(CvN) 1582; ν(ClO 4 ) 1094 cm −1 . Anal. found: C, 53.8; H, 3.9; N, 1.8; S, 4.1%, C 34 H 31 ClNO 6 PPdS (754.53 g mol −1 ) requires C, 54.1; H, 4.1; N, 1.9; S, 4.3%. [Pd{3-Me-4-OMeC 6 H 2 C(H)vN[2-(SMe)C 6 H 4 ]}(PPh 3 )][ClO 4 ] 2b. Orange solid. Yield: 80%. 1 H NMR (400 MHz, acetone-d 6 )δ 9.25 (d, 4 J P–H = 9.1 Hz, 1H, HCvN), 8.06 (d, 3 J= 8.6 Hz, 1H, H11), 7.85 (dd, J= 12.4, 8.0 Hz, 6H), 7.74–7.56 (m, 9H), 7.51 (d, J= 6.8 Hz, 11H), 7.43 (s, 1H, H2), 6.84 (t, J= 7.9 Hz, 1H, H9), 6.62 (t, J= 7.9 Hz, 1H, H10), 6.05 (d, 4 J P–H = 4.3 Hz, 1H, H5), 2.95 (s, 3H, OMe), 2.26 (s, 3H, Me), 2.12 (s, 3H, SMe). 31 P-NMR (400 MHz, acetone-d 6 )δ37.49. IR cm −1 ν(CvN) 1582; ν(ClO 4 ) 1091. Anal. found: C, 55.1; H, 4.1; N, 1.9; S, 4.4%, C 34 H 31 ClNO 5 PPdS (738.53 g mol −1 ) requires C, 55.3; H, 4.2; N, 1.9; S, 4.3%. [Pd{3,4-(OCH 2 CH 2 O)C 6 H 2 C(H)vN[2-(SMe)C 6 H 4 ]}(PPh 3 )][ClO 4 ] 2c. Orange solid. Yield: 85%. 1 H NMR (400 MHz, acetone-d 6 )δ 9.30 (d, 4 J P–H = 9.0 Hz, 1H, HCvN), 8.10 (d, 3 J= 8.3 Hz, 1H, H11), 8.06–7.97 (m, 6H), 7.78–7.49 (m, 9H), 7.46 (t, 3 J= 7.6 Hz, 1H, H10), 7.36 (m, 1H, H9), 7.09 (s, 1H, H2), 7.02 (s, 1H, H2), 5.95 (d, 4 J P–H = 5.0 Hz, 1H, H5), 4.17–4.10 (m, 4H, OCH 2 CH 2 O), 2.14 (s, 3H, SMe). 31 P-NMR (400 MHz, acetone-d 6 )δ38.54. IR cm −1 ν(CvN) 1576; ν(ClO 4 ) 1094. Anal. found: C, 54.5; H, 3.9; N, 2.1; S, 4.1%, C 34 H 29 ClNO 6 PPdS (752.51 g mol −1 ) requires C, 54.3; H, 3.9; N, 1.9; S, 4.3%. Reactivity of 2-methylthio aniline Route a: Palladium acetate was introduced into a carousel tube fitted with a stirring bar. 10 mL of toluene are added, and a partial dissolution of palladium salt is observed. Methylthioaniline is then introduced, and it is observed that the solution becomes orange. It is allowed to react with stirring at 50 °C for 24 h, after which the formation of a yellow solid is observed within the solution that is separated by centrifugation. The supernatant is brought to dryness, resulting in an orange solid. 1 H NMR (400 MHz, acetone-d 6 )δ7.27 (d, 3 J= 7.6 Hz, 1H), 7.02 (t, 3 J= 7.7 Hz, 1H), 6.77 (d, 3 J= 8.1 Hz, 1H), 6.59 (t, 3 J= 7.5 Hz, 1H), 4.91 (d, 3 J= 10.2 Hz, 2H), 2.31 (s, 3H). Route b: In a carousel tube fitted with a stirring bar sodium tetrachloropalladate was added in methanol (10 mL) and a reddish solution was formed; which quickly changes to yellow upon addition of methylthioaniline. The reaction mixture was stirred for 24 h and a white solid formed was separated by centrifugation, after which the resulting solution was reduced to low volume to give an orange solid. 1 H NMR (400 MHz, DMSO-d 6 )δ7.84 (d, 3 J= 7.7 Hz, 1H), 7.48 (t, 3 J= 7.5 Hz, 1H), 7.42 (t, 3 J= 7.5 Hz, 1H), 7.33 (d, 3 J= 7.9 Hz, 1H), 7.18 (d, 3 J= 7.7 Hz, 1H), 6.97 (t, 3 J= 7.7 Hz, 1H), 6.68 (d, 3 J= 8.0 Hz, 1H), 6.53 (t, 3 J= 7.5 Hz, 1H), 5.16 (s, 2H, NH), 2.84 (s, 3H, SMe), 2.29 (s, 3H, SMe). Preparation of the diphosphine palladacycles [Pd{4-OMeC 6 H 3 C(H)vN[2-(SMe)C 6 H 4 ]}(PPh 2 CH 2 PPh 2 -P)] (ClO 4 ) (3d). Silver perchlorate (10.4 mg, 0.05 mmol) was added to a suspension of the cyclometallated complex 1a (20 mg, 0.05 mmol) in acetone (15 cm 3 ). The mixture was stirred for 4 h at r.t. and filtered over Celite to remove the silver chloride precipitate. PPh 2 CH 2 PPh 2 (19 mg, 0.05 mmol) was added to the filtrate and the solution stirred for 24 h at r.t., the solvent was removed and the residue was recrystallized from dichloromethane/hexane. Orange solid. Yield 78%. 1 H NMR (400 MHz, CDCl 3 )δ8.88 (d, 1H, HCvN, 4 J P–H = 8.4 Hz), 7.30–7.80 (m, 20H, PPh 2 ); H2, 7.70–7.00 (H10–H12 hidden by the resonance of aromatic phosphine system), 7.15 (d, 1H, H9), 6.61 (d, 1H, H3, 3 J(H2H3) = 7.5 Hz), 5.84 (s, 1H, H5), 4.19 (ta, 2H, PCH 2 P, 2 J(HP) = 2.4 Hz), 3.22 (s, 3H, OCH 3 ), 2.07 (s, 3H, SCH 3 ). 31 P NMR (400 MHz, CDCl 3 )δ−23.60 (d, 2 J(PP) = 51.5 Hz); 31.30 (d, 2 J(PP) = 51.5 Hz). IR cm −1 ν(CvN) 1598; ν(ClO 4 ) 1093. Anal. found: C, 56.8; H, 4.3; N, 1.7; S, 4.3%, C 40 H 36 ClNO 5 P 2 Pd S (846.60 g mol −1 ) requires C, 57.0; H, 4.2; N, 1.6; S, 3.8%. [Pd{2,4-(OMe) 2 C 6 H 3 C(H)vN[2-(SMe)C 6 H 4 ]}(PPh 2 CH 2 P(Ph 2 ) W(CO) 5 -P)](ClO 4 ) (4d). To a suspension of 1e (20 mg, 0.05 mmol) in acetone (15 cm 3 ). AgClO 4 was added. The mixture was stirred for 4 h, after which time the silver chloride formed was filtered offthrough Celite. PPh 2 CH 2 P(Ph 2 )W(CO) 5 (11 mg, 0.025 mmol) was added to the filtrate and the solution stirred for 4 h; reducing to low volume gave a solid which was filtered offand dried. Yellow solid. Yield 53% (1200.52). Calc. found. 1 H NMR (400 MHz, CDCl 3 )δ8.90 (d, 1H, HCvN, 4 J P–H = 7.6 Hz), 7.70–7.00 (H9–H12 hidden by the resonance of aromatic phosphine system), 6.42 (d, 2 J(PP) = 72.0 Hz, 1 J(PW) = 247.9 Hz), 6.02 (d, 1H, H3, 4 J(H3H5) = 3.2 Hz), 5.55 (dd, 1H, H5, 4 J(H5H3) = 3.2 Hz, 4 J(H5P) = 7.1 Hz), 4.93 (t, 1H, CH 2 , 2 J(HP) = 9.3 Hz, 2 J(HP) = 11.5 Hz), 3.98 (dd, 1H, CH 2 , 2 J(HP) = 6.3 Hz, 2 J(HP) = 11.7 Hz), 3.82 (s, 3H, OCH 3 ), 3.40 (s, 3H, OCH 3 ), 1.70 (s, 3H, SCH 3 ). 31 P NMR (400 MHz, CDCl 3 )δ26.6 (d, 2 J(PP) = 72.0 Hz); IR cm −1 ν(CvN) 1583; ν(ClO 4 ) 1095. Anal. found: C, 45.8; H, 3.3; N, 1.7; S, 3.2%, C 46 H 38 ClNO 11 P 2 PdSW (1200.52 g mol −1 ) requires C, 46.0; H, 3.2; N, 1.2; S, 2.7%. Results and discussion For the convenience of the reader the compounds and reactions are shown in Schemes 1–3. The compounds described in this paper were characterized by elemental analysis (C, H, N, S), and by IR spectroscopy, and by 1 H, 31 P–{ 1 H} spectroscopy and, in part, crystal structure analysis (see Experimental, Table 1 and Fig. 1–5). Dalton Transactions Paper This journal is © The Royal Society of Chemistry 2024 Dalton Trans.,2024,53,9680–9691 | 9683 Open Access Article. Published on 19 April 2024. Downloaded on 7/10/2024 7:49:16 AM. This article is licensed under a Creative Commons Attribution-NonCommercial 3.0 Unported Licence. View Article Online The Schiffbase ligands a–fwere prepared by reaction of 2-thiomethylaniline with the corresponding aldehyde to give pure air-stable solids which were fully characterized. Distinctive of the spectrum of dwere the two virtual doublets stemming from the aromatic AA′XX′spin system with N= 8.0 ppm. Treatment of the ligands with Li 2 [PdCl 4 ]/NaAcO in methanol gave the palladacycles 1a–1c (Scheme 1) and 1d–1f (Scheme 3) that were isolated as air-stable solids with the ligand in a tridentate [C,N,S] coordination mode; preparative details and characteristic microanalytical and spectroscopic data are given in the Experimental section. Noteworthy to mention are the shift of the ν(CvN) stretch to lower wavenumbers by ca.40cm −1 in the IR spectra, and absence of the C(6)– H resonance in the NMR spectra; 43 also, the SMe resonance was downfield shifted in the 1 H NMR spectra, ca. 0.4 ppm, in agreement with Pd–S coordination, and the metallated ligand of 1d showed the absence of the AA′XX′system consequent on Pd–C bond formation. Crystal structure of 1b Suitable crystals were grown by slow evaporation of a chloroform solution. The crystal structure of 1b (Fig. 1 and Table 1) consists of molecules with the palladium(II) atom bonded in a slightly distorted square-planar environment to four different donor atoms, the aryl C(6) carbon, the iminic N(1) nitrogen, and the S(1) sulfur atoms, of the tridentate iminic and to the chlorine atom Cl(1). The sulfur atom in SMe becomes a chiral center upon metalation, and in the structure there is a racemic mixture of both enantiomers. The angles between adjacent atoms in the palladium coordination sphere are ca. 90° with the most noticeable distortion in the N(1)2Pd(1)2C(6) angle of 81.7(2)°, a consequence of chelation; the sum of angles around the palladium atom is 360.03°. All bond lengths are within the expected range, with allowance for Pd(1)2C(1) length, of 2.044 (4) Å, shorter than the expected value of 2.081 Å 44 suggesting some degree of multiple bond character in the Pd2C(aryl) linkage. 45 Reaction of 1a–1c with PPh 3 /AgClO 4 gave complexes 2a–2c, after abstraction of the chloride ion as AgCl, which were fully characterized (see Experimental). Attempts to produce species Scheme 1 Reaction sequence leading to the synthesis of the compounds. Scheme 2 Reactivity of 2-thiomethyl aniline with differing palladium reagents. Paper Dalton Transactions 9684 |Dalton Trans.,2024,53,9680–9691 This journal is © The Royal Society of Chemistry 2024 Open Access Article. Published on 19 April 2024. Downloaded on 7/10/2024 7:49:16 AM. This article is licensed under a Creative Commons Attribution-NonCommercial 3.0 Unported Licence. View Article Online with simultaneous linkage of the phosphine and chloride ligands to the metal were to no avail; this is in keeping with a rather strong Pd–S bond. The IR spectra showed absence and of the ν(Pd–Cl) band; whilst the 1 H NMR spectra the H(5) was upfield shifted and coupled to the phosphorus resonance. To study the suitability of other metallating agents a slightly different synthetic approach was tested with ligands a– c; this allowed disclosure of a new performance of the ligands and complexes. Thus, treatment of ligands a–cwith Na 2 [PdCl 4 ]/NaAcO in methanol gave a solution containing the 1a–1c complexes, with analogous spectroscopic features as those described above, plus the starting aldehyde and amine, for which the 1 H NMR spectra showed the signals for the HCvO, NH 2 and SMe resonances ca. 10, 6.7 and 2.3 ppm, respectively, together with other aromatic resonances (mixtures type A). This did not seem to be unusual because in the previous reactions using Li 2 [PdCl 4 ] as metal salt, prior to addition of the base, aliquots of the reaction mixture were taken and some free aldehyde was observed due to partial hydrolysis; however, in those cases after addition of NaAcO and ensuing work up the final compounds were obtained pure (vide supra). Then, treatment of the said mixture A with PPh 3 /AgClO 4 yielded compounds 2a–2c impurified with free aldehyde and amine (mixtures type B). To separate the palladacycles and confirm the alternative use of the sodium salt as a metallating agent, recrystallization was performed for both types of mixtures. Crystal structure of 5 Suitable crystals of mixture A were grown from a chloroform solution, labelled 5. The crystal structure of 5(Fig. 2 and Table 1) consists of molecules with the palladium(II) atom Scheme 3 Reaction sequence leading to the compounds with diphosphine. Dalton Transactions Paper This journal is © The Royal Society of Chemistry 2024 Dalton Trans.,2024,53,9680–9691 | 9685 Open Access Article. Published on 19 April 2024. Downloaded on 7/10/2024 7:49:16 AM. This article is licensed under a Creative Commons Attribution-NonCommercial 3.0 Unported Licence. View Article Online bonded in a slightly distorted square-planar environment to two mutually perpendicular pairs of [O,O] and [N,S] donors, pertaining to bridging acetate and chelating 2-thiomethyl- anilide ligands, respectively; the nitrogen atoms in turn act as bridging donors between two palladiums. The nitrogen atoms are arranged in a square-planar geometry and in turn act as bridging donors holding the palladium atoms at a midway distance between each pair of nitrogens to give an eight-mem- bered ring of alternating Pd/N centers. Thus, the palladium coordination planes are set as two pairs of mutually facing parallel planes ca. 90° to the Pd 4 N 4 ring. We reasoned that mixture B should produce either crystals of 2a–2c, as appropriate, or a structure analogous to 5 depending on whether or not the acetate ligands were lost in the corresponding preparation. Again, the experimental facts show that an absolutely distinctive structure was obtained: a trinuclear crystal void of any acetate ligands, labelled 6. Crystal structure of 6 Suitable crystals were grown from mixture B from a DMSO-d 6 solution, labelled 6. The crystal structure (Fig. 3 and Table 1) consists of a trinuclear molecule with a central Pd 3 N 3 six-mem- bered ring of alternating palladium and nitrogen atoms in a chair conformation, with the Pd(2) and N(10) atoms pointing to opposite directions from the Pd(1)N(8)N(9)Pd(3) plane (Fig. 5b). Each palladium atom is bonded to a chelating bidentate [N,S] 2-thiomethylanilide, that in turn also coordinates as a bridging ligand between two metal atoms via the nitrogen donor. The fourth coordination site at each palladium is occupied by a chloride ligand trans to nitrogen for the three metal centers. The palladium coordination planes [S(1)N(8)Cl(1)Pd (1)N(10)] (plane 1), [S(2)N(8)Cl(2)Pd(2)N(9)] (plane 2) and [S(3) N(9)Cl(3)Pd(3)N(10)] (plane 3) are set as follows: 1^2 83.44°; 1^3 77.08°; 2^3 79.91°. In view of this unexpected behavior of the amine ligand stemming from partial hydrolysis of the parent Schiffbase, we sought out to study the behavior of free 2-methyl- thioaniline itself in order to determine if compounds 5and 6were produced only from the corresponding palladacycles, or if it was solely dependent on the presence of the free amine. For such a purpose 2-thiomethylaniline was treated independently with Pd(OAc) 2 in toluene or with Na 2 [PdCl 4 ] in methanol (see Scheme 2 and Experimental for preparative details). The former process gave only the free amine, as was determined by 1 H NMR spectroscopy. However, in the latter case the 1 H NMR spectrum shows there are two singlets assignable to the SMe groups and two sets of aromatic peaks containing four doublets and four triplets in agreement with a four-spin system of an ortho-substituted phenyl ring. This is a differing situation from that found for compounds 5and 6, where the Table 1 Crystallographic data for 1b,5–8 Compound 1b 5 6 7 8 Empirical formula C 16 H 16 ClNOPdS C 17 H 20 Cl 4 N 2 O 6 Pd 2 S 2 C 25 H 36 Cl 3 N 3 O 2 Pd 3 S 5 C 31 H 35 Cl 13 N 4 Pd 4 S 4 C 78 H 66 Cl 2 N 2 O 22 PdPd 3 S 2 W 2 Formula weight 412.245 767.131 996.518 1479.647 2329.12 Temperature/K 100.0 100.0 100.0 100.00 100.0 Crystal system Monoclinic Triclinic Monoclinic Orthorhombic Triclinic Space group P2 1 /cP1 ˉP2 1 /n Pbca P1 ˉ a/Å 8.1340(2) 11.6987(6) 9.6057(5) 10.6947(8) 10.8665(13) b/Å 11.6466(3) 15.0875(8) 19.0596(10) 22.0850(16) 12.0797(14) c/Å 17.0711(4) 18.3377(9) 19.8471(11) 40.285(3) 19.070(2) α/° 90 105.262(3) 90 90 72.291(7) β/° 101.9138(10) 104.871(3) 91.4728(17) 90 89.037(7) γ/° 90 107.653(4) 90 90 78.172(7) Volume/Å 3 1582.37(7) 2769.0(3) 3632.4(3) 9515.0(12) 2331.2(5) Z44 4 81 ρ calc. /g cm −3 1.730 1.840 1.822 2.066 1.659 μ/mm −1 1.471 15.748 2.006 2.425 3.262 F(000) 821.5 1518.5 1961.1 5733.3 1136 Crystal size/mm 3 0.156 × 0.127 × 0.092 0.08 × 0.03 × 0.02 0.14 × 0.09 × 0.05 0.09 × 0.07 × 0.03 0.200 × 0.090 × 0.030 Radiation Mo Kα(λ= 0.71073) Cu Kα(λ= 1.54178) Mo Kα(λ= 0.71073) Mo Kα(λ= 0.71073) Mo Kα(λ= 0.71073) 2θ/° 4.88 to 77.14 6.62 to 140.14 4.74 to 56.76 4.32 to 56.68 1.810 to 26.445 Index ranges −14 ≤h≤14, −20 ≤k≤19, −29 ≤l≤ 29 −14 ≤h≤14, −18 ≤k≤18, −22 ≤l≤22 −12 ≤h≤12, −25 ≤k≤25, −25 ≤l≤26 −14 ≤h≤14, −29 ≤k≤29, −33 ≤l≤53 −13 ≤h≤13, −15 ≤k≤15, −23 ≤l≤23 Reflections collected 63 757 68 334 86 053 98 993 70 681 Independent reflections 8909 [R int = 0.0353, R sigma = 0.0233] 10 523 [R int = 0.1983, R sigma =0.1049] 9079 [R int = 0.0378, R sigma = 0.0198] 11 826 [R int = 0.0686, R sigma = 0.0392] 9506 [R int = 0.1012] Data/restraints/parameters 8909/0/193 10 523/0/602 9079/24/459 11 826/24/574 9506/439/550 Goodness-of-fit on F 2 1.037 1.020 1.050 1.045 1.087 Final Rindexes [I≥2σ(I)] R 1 = 0.0232, wR 2 = 0.0510 R 1 = 0.0676, wR 2 = 0.1638 R 1 = 0.0328, wR 2 = 0.0737 R 1 = 0.0727, wR 2 = 0.1316 R 1 = 0.0762, wR 2 = 0.1540 Final Rindexes [all data] R 1 = 0.0312, wR 2 = 0.0547 R 1 = 0.1213, wR 2 = 0.2051 R 1 = 0.0370, wR 2 = 0.0764 R 1 = 0.0832, wR 2 = 0.1368 R 1 = 0.1130, wR 2 = 0.1649 Largest diff. peak/hole/e Å −3 0.73/−1.16 1.59/−1.82 3.16/−2.83 1.63/−1.91 2.303/−2.307 Paper Dalton Transactions 9686 |Dalton Trans.,2024,53, 9680–9691 This journal is © The Royal Society of Chemistry 2024 Open Access Article. Published on 19 April 2024. Downloaded on 7/10/2024 7:49:16 AM. This article is licensed under a Creative Commons Attribution-NonCommercial 3.0 Unported Licence. View Article Online 2-thiomethylanilide ligands were in equivalent chemical environments, pointing to two types of non-equivalent amine molecules that are present in the final compound. Fortunately, single-crystals could be obtained to clarify this finding and the result is even more fascinating than for structures 5and 6 (vide infra). Crystal structure of 7 Suitable crystals were grown from a chloroform solution, labelled 7. The crystal structure (Fig. 4 and Table 1) consists of four palladium atoms, four chloride and four 2-thiomethyl- anilide ligands displayed such that there are three types of palladium coordination environments: 2 + 1 + 1. The aniline moieties are linked to the Pd(1), Pd(2) and Pd(4) atoms in a bidentate [N,S] fashion and the four palladium atoms are bonded together via the nitrogen from bridging 2-MeC 6 H 4 NH 2 -Nunits; the chlorine atoms complete the coordination sphere at the metal as terminal ligands. Thus, Pd(1) is bonded to two chelating [N,S] aniline ligands with the donor atoms in a cis geometry; Pd(2) and Pd(4) to one chelating amine, a terminal chlorine atom and a nitrogen atom from an adjacent organic ligand; Pd(3) to two mutually trans terminal chlorine atoms and two nitrogen donors form nearby amine ligands also in a trans arrangement. All of which results in a Pd 4 N 4 eight-mem- bered ring of alternating palladium and nitrogen atoms. The palladium coordination planes [Pd(1)N(1)N(4)S(1)S(4)] (1), [Pd (2)N(1)N(2)S(2)Cl(1)] (2), [Pd(3)N(2)N(3)Cl(2)Cl(3)] (3) [Pd(4)N (3)N(4)S(3)Cl(4)] (4) [1^2 89.59°; 1^3 87.60°, 1^4 86.55°, 2^3 85.92°; 3^4 85.81°; 2^4 8.99°] are angled ca. 90°, save for planes 2 and 4 which are close to a parallel disposition. Next, we attempted to study the behavior of the 1a–1f class complexes with diphosphines to determine whether they would give species analogous to the thiosemicarbazone-[C,N,S] palladacycles we have described in the past, i.e., complexes with a mono-coordinated diphosphine and also the ensuing dinuclear compounds with the diphosphine ligand bridging two metal centers; or if alternatively, and given the results depicted above, they would evolve to unprecedented multinuclear compounds; for which purpose we chose compound 1d and the diphosphine dppm, Ph 2 PCH 2 PPh 2 . Hence, treatment of 1d with dppm in 1 : 1 molar ratio and NaClO 4 gave the hoped for complex 3d asapureair-stablesolid, which was fully characterized. The 31 P NMR spectrum displayed two doublets at −23.6 and 31.3 ppm, for the two inequivalent phosphorus nuclei. The resonance at lower frequency was assigned to the non-coordinated phosphorus nucleus; whereas the one at higher frequency was assigned to the phosphorus nucleus bonded to palladium. The HCvN resonance was a doublet coupled to the trans phosphorus nucleus ( 4 J(HiP) = 8.4 Hz). Both the MeOandSMe resonances were shifted to lower frequency ca. 0.6 and 0.7 ppm respectively, due to shielding by the phosphine phenyl rings. The proton signal was an apparent triplet from the AA′XX′four spin system P(CH 2 )Pwith an Nvalue of 2.4 Hz. Attempts to prepare the heterobimetallic complex 4d by treatment of 3d with [W(CO) 5 (THF)] gave an untreatable mixture which was not further investigated. Likewise, reaction of 3d with other substrates bearing labile ligands such as [Fe(CO) 4 (THF)] and [Pd (Cl) 2 (PhCN) 2 ], to yield the corresponding dinuclear species were also deemed unsuccessful. Alternatively, reaction of 1d with [W (CO) 5 {Ph 2 PCH 2 PPh 2 –P}] did produce the expected compound 4d Fig. 1 ORTEP drawing of compound 1b with thermal ellipsoid plot shown at 50% probability level. Hydrogen atoms and solvent molecules have been omitted for clarity. Selected bond distances (Å) and angles (°): Pd(1)–C(1) 1.9936(11), Pd(1)–N(1) 2.0039(9), Pd(1)–S(1) 2.3987(3), Pd(1)– Cl(1) 2.2963(3), S(1)–Pd(1)–Cl(1) 98.815(10), N(1)–Pd(1)–S(1) 84.63(3), N(1)–Pd(1)–Cl(1) 175.43(3), C(1)–Pd(1)–S(1) 166.53(3), C(1)–Pd(1)–Cl(1) 94.65(3), C(1)–Pd(1)–N(1) 81.91(4). Fig. 2 ORTEP drawing of compound 5with thermal ellipsoid plot shown at 50% probability level. Hydrogen atoms and solvent molecules have been omitted for clarity. Selected bond distances (Å) and angles (°): Pd(01)–S(005) 2.262(3), Pd(01)–N(00N) 2.065(8), Pd(01)–N(00M) 2.032(9), Pd(01)–O(00I) 2.042(8), N(00N)–Pd(01)–S(005) 99.5(3), N(00N)–Pd(01)–O(00I) 88.1(3), N(00M)–Pd(01)–O(00I) 87.0(3), N(00M)– Pd(01)–S(005) 85.7(3); Pd(02)–O(00G) 2.044(8), Pd(02)–N(00N) 2.014(9), Pd(02)–N(00M) 2.063(9), Pd(02)–S(006), 2.257(3), N(00N)– Pd(02)–S(006) 86.2(3), N(00N)–Pd(02)–O(00G) 91.2(4), N(00M)– Pd(02)–O(00G) 88.4(3), N(00M)–Pd(02)–S(006) 94.4(3). Dalton Transactions Paper This journal is © The Royal Society of Chemistry 2024 Dalton Trans.,2024,53, 9680–9691 | 9687 Open Access Article. Published on 19 April 2024. Downloaded on 7/10/2024 7:49:16 AM. This article is licensed under a Creative Commons Attribution-NonCommercial 3.0 Unported Licence. View Article Online