Electron-rich metal complexes for C02 and CS2 incorporation

Pu e & Appl. Chem., Vol. 61, No. 10, pp. 1701-1706, 1989. P in ed in G ea B i ain. @ 1989 IUPAC Elec on- ich me al complexes o C02 and CS2 inco po a ion E nes 0 Ca mona, Juan Cimpo a, Miguel A. MuRoz, Ma ga i a Paneque and Manuel L. Po eda Depa amen o de Quimica Ino ginica-Ins i u o de Ciencia de Ma e iales, Facul ad de Quimica, Uni e sidad-CSIC, Apa ado 553, 41071 Se illa, Spain Abs ac - The dihap o coo dina ion o wo molecules o ca bon dioxide o a squa e-plana MoP2(P-P) agmen (P=monoden a e-, P-P=biden a e phosphi- ne ligands) can occu in se e al ways gi ing ise o di e en con o me s. Compounds o his ype ha e been p epa ed and hei spec oscopic p ope - ies in es iga ed by a iable empe a u e 'H and 31P NMR s udies. The o - ma ion o e hylene complexes ela ed o Mo(C2H4)2(PMe3)4, 6, and he s udy o hei eac i i y owa ds ca bon dioxide and ca bon disulphide is also desc ibed. In pa icula , compound 6 induces a head- o- ail dime iza ion o ca bon disulphide wi h o ma ion o a Mo(II)-C$4 linkage, which, in he p esence o ca bon monoxide, unde goes a symme ic, oxida i e up u e, which p oduces a Mo(0) complex and wo molecules o ca bon disulphide. The inse ion eac ions o ca bon dioxide and o he unsa u a ed molecules in o he nickel-ca bon bonds o he nickelacyclopen ene complexes 9 ha e been in es iga ed and di e en o ganic p oduc s isola ed by means o simple o sequen ial inse ion eac ions. INTRODUCTION The eac ions o ca bon dioxide wi h ansi ion me al complexes ha e been ex ensi ely in es- iga ed in he las decade. These in es iga ions ha e led o he isola ion o some s able ansi ion me al-ca bon dioxide complexes, as well as o he obse a ion o ca bon-ca bon coupling eac ions be ween ca bon dioxide and a a ie y o o ganic subs a es ( e s. 1-5). Conside able p og ess has been made in he unde s anding o he in e ac ion o ca bon dioxide wi h ansi ion me als bu many impo an aspec s o his chemis y emain li le explo ed o unde de eloped, so ha ca bon dioxide chemis y is s ill a p omising a ea o esea ch. In o de o o e come he di icul ies e y o en encoun e ed in he s udy o he eac ions o ca bon dioxide wi h ansi ion me als, ca bon disulphide and o he ela ed molecules ( e . 6) ha e been used as models o ca bon dioxide chemis y. Howe e , he esul s ob ained o da e clea ly show ha hese molecules exhibi a e y dis inc chemical beha iou which only e y a ely pa allels ca bon dioxide chemis y. In pa icula , ca bon disulphide displays a e y ich chemis y o much in insic academic in e es . In his con ibu ion we wish o epo some eac ions o ca bon dioxide wi h complexes o molybdenum and nickel, ha lead o adduc o ma ion o o inse ion in o a me al-ca bon bond. The eac ions o hese complexes wi h CS2 a e also desc ibed. CARBON DIOXIDE AND CARBON DISULPHIDE COMPLEXES OF MOLYBDENUM Ca bon dioxide complexes con aining chela ing phosphine ligands Coo dina ion o ca bon dioxide in i s in ac o m o a ansi ion me al is a a e esul and he numbe o s uc u ally cha ac e ized complexes is he e o e e y limi ed. A a iance wi h he beha iou ound o o he ca bon dioxide complexes, he bis-ca bon dioxide adduc ans-Mo(C02)2(PMe3)4, (l), has been epo ed o unde go a acile subs i u ion o one o he coo dina ed PMe3 g oups by an isocyanide ligand, wi h o ma ion o uns,me -Mo(C02)2(CNR)(P Me3)3 emp s o subs i u e a second phosphine by hea ing a 5O-6O0C, in he p esence o an excess o he isocyanide, lead o loss o ca bon dioxide. We ha e now ound ( e . 8) ha chela ing diphosphine ligands e ec subs i u ion o wo molecules o ime hylphosphine o complex 1, wi hou change in he coo dina ion mode o he ca bon dioxide g oups. Compounds,Za-Zb, a e o med, as shown in eac ion (1). The new complexes a e yellow c ys alline solids which dis- play IR and NMR spec oscopic p ope ies e y simila o hose epo ed o he pa en com- pound 1. Ou in e es in complexes 2 was mainly concen a ed in he ollowing poin s: i) assuming ha he coo dina ed C02 ligands a e s agge ed wi h espec o one ano he and ( e , 7). Subs i u ion o he ca bon dioxide ligands is no obse ed, al hough a - 1701 B ough o you by | Biblio eca de la Uni e sidad de Se illa Au hen ica ed Download Da e | 9/10/19 10:14 AM 1702 E. CARMONA e a/. eclipsing he P-Mo-P ec o s o he equa o ial plane, as p edic ed heo e ically o 1 ( e . 9) and demons a ed by X- ay s udies o he mono-isocyanide de i a i e ( e . 7), he e could be h ee di e en con o ma ions in compounds 2, as ep esen ed in s uc u es 3-5. Would any 3 4 5 o hese con o ma ions be a ou ed in solu ion and in he solid s a e?, ii) compounds 2, as he pa en complex 1, a e luxional, and he p ocess esponsible o he obse ed changes in he NMR spec a is o a ion a ound he molybdenum-ca bon dioxide bond axis. Since he e a e wo molecules o ca bon dioxide coo dina ed o he molybdenum a om, he ques ion a ises as o wha is he na u e o he o a ion p ocess. Va iable empe a u e NMR s udies p o ide some clues o bo h ques ions. The oom empe a u e 31P{1H1 NMR o complex 2a, consis s o wo e y b oad and ea u eless humps, which gi e no use ul in o ma ion wi h ega ds o he s uc u e o he compound. Upon cooling some changes a e obse ed, and a -9OOC ou di e en se s o esonances (AMNX spin sys em) appea . This is in acco d wi h s uc u e 2 and no wi h 2 o 4. Wi h espec o he second o he abo e ques ions, namely he na u e o he luxional p ocess, a clea dis inc ion be ween he possi- ble mechanisms canno be achie ed wi h p esen da a. In he low empe a u e limi (-75OC) he 'H NMR spec um o 2a consis s o wo pa ially supe imposed double s o he PMe3 ligands, as well as o ou double s, one o each o he dmpm me hyl g oups, in acco d wi h he igid s uc u e 5 p oposed o hese complexes. Upon wa ming he spec um simpli ies and a 4OoC i consis s o one double o he ime hylphosphine g oups and wo double s o he me hyl p o ons o he chela ing phosphine ligand, in ag eemen wi h a conce ed, bu no wi h a an- dom o a ion. Finally, in acco d wi h hese obse a ions, he 31P{1H1 NMR spec um o com- pounds 2 consis s, a high empe a u es (60-80°C), o a pa e n o lines cha ac e is ic o an AA'XX' spin sys em ( e . 8). Wi h he aim o ob aining new ca bon dioxide complexes, he eac ions o a ious dini ogen complexes o molybdenum, p epa ed as summa ized in eac ions (2)-(4), wi h C02 ha e been s u- "Mo(N2 )3(PE~3 )3" + PME~ - =-Mo( N2 )2 (PME~) 3( PET^) + died. Reac ion (3) p oduces in ac a mix u e o he is-dini ogen complex and he dini o- gen b idged species [Mo(N2)2(PE 3)2]2(~-N2), w i en in a simpli ied o m as shown. Ac ion o C02 upon solu ions o hese complexes p o ide only ca bona e complexes, i. e., he p oduc s o he so-called educ i e disp opo iona ion o ca bon dioxide, and he e o e hei in es i- ga ion has no been pu sued any u he ( e . 10). B ough o you by | Biblio eca de la Uni e sidad de Se illa Au hen ica ed Download Da e | 9/10/19 10:14 AM Elec on ich me al complexes o CO, and CS, inco po a ion 1703 Reac ions o anaM~(C~H~)~(PMe~)~, (61, and ela ed complexes wi h ca bon dioxide and ca bon disulphide We ha e ecen ly epo ed ha ca bon dioxide eac s wi h one o he coo dina ed e hylene li- gands o complex 6, o ming a new C-C bond ( e . 11). The p oduc o his eac ion is a binu- clea molybdenum complex which con ains wo b idging ac yla e ligands ( e . 12), and he a- P cile ac i a ion o ca bon dioxide by complex 6 is p obably a consequence o he elec on- ich na u e o he me al cen e and o he a ailabili y o a acan coo dina ion posi ion by aci- le dissocia ion o one o he ime hylphosphine ligands ( e . 11). In o de o gain u he in o ma ion on his ema kable ans o ma ion o he ela ed sys ems ha e been in es iga ed, eac ions (5)-(7): P-P= DMPM, DMPE i) a emp s o p epa e he p opylene analogue o 6 lead ins ead o a hyd ido ally1 species ( e . 13) which eac s wi h ca bon dioxide wi h e olu ion o p opylene and o ma ion o 1 and o he p oduc s ( e . 10). ii) PMe3 subs i u ion in 6 by he Il-acid ligands CO o CNR ( e . 14) a o ds new e hylene com- plexes as ep esen ed in eac ion (6). No unexpec edly, hei eac i i y owa ds ca bon dio- xide does no pa allel ha o 6. iii) compounds ela ed o 6 con aining chela ing phosphine ligands can be p epa ed as depic- ed in equa ion (7). These compounds a e su p isingly ine owa ds ca bon dioxide. Fo ins- ance, he dmpe de i a i e can be eco e ed unchanged a e hea ing a 6OoC, o se e al ho- u s, in e ahyd o u an, unde 2-3 a m o ca bon dioxide. The lack o eac i i y in his case e lec s p obably he non a ailabili y o a acan coo dina ion posi ion. I was also o in e es o asce ain i o he he e ocumulenes, in pa icula ca bon disulphi- de, would unde go simila ans o ma ions. Addi ion o ca bon disulphide o solu ions o com- plex 6 p oduces a black solid o composi ion Mo(C~S,)(C,H,)(PM~~)~, (7), which has he PMe3 g oups in a me idional dis ibu ion. The e hylene ligand anysoch onous me hylenic p o ons, while he wo CS2 molecules gi e ise o a single and a qua e (I3C en iched sample o 7, 227 and 293 ppm, espec i ely), sugges ing ha one o he ca bon disulphide g oups is C-bonded o he me al a om. The bonding mode o he C2S4 uni has been de e mined by X- ay s udies ( e . 15) which show he wo molecules o CS2 ha e linked o a head- o- ail dime . Fo ma ion o 7 can he e o e be ep esen ed as in equa ion (8). has equi alen CH2 moie ies bu 7 B ough o you by | Biblio eca de la Uni e sidad de Se illa Au hen ica ed Download Da e | 9/10/19 10:14 AM 1704 E. CARMONA e a/. Me allocyclic complexes o his ype a e o en p oposed as in e media es in he me al-p omo- ed educ i e disp opo iona ion o ca bon dioxide and ela ed molecules, al hough conclusi e e idence has ne e been ob ained ( e . 16). Fu he mo e, he e is a su p ising lack o s u- dies aimed a he in es iga ion o he chemical eac i i y o hese uni s. Compound 7 exhi- bi s a high he mal s abili y and does no decompose, no p oduces he disp opo iona ion p o- duc s, CS and CS32-, a e hea ing a 120°C o se e al hou s. An unexpec ed eac ion occu s wi h ca bon monoxide unde ela i ely mild condi ions (5OoC, 2 a m). As shown in Scheme I, symme ic oxida i e up u e o he C2S4 uni is obse ed, wi h educ ion o he molybdenum(0) complex 8, i. e., he e e se o he educ i e di ne iza ion eac ion. These esul s no only demons a e a new ype o eac i i y o hese me alacyclic uni s, bu ques ion hei p oposed in e mediacy in he ansi ion me al induced educ i e disp opo iona ion o he e ocumulenes. INSERTION CHEMISTRY OF THE NICKELACYCLOPENTENE COMPLEX Ni[CH2C(Me)2-O-C6H41(PMeJ)2 9a. REACTIONS WITH CARBON DIOXIDE, CARBON DlSULPHlDE AND OTHER UNSATURATED MOLECULES The nickelacyclopen ene complex 9a has a ich inse ion chemis y and eac s wi h ca bon mo- noxide, ca bon dioxide, ca bon disulphide and o he unsa u a ed molecules ( e . 17) wi h o - ma ion o a a ie y o o ganic and me allo-o ganic p oduc s. The in e ac ion o 9a wi h CO and PhCaCPh, unde ambien condi ions, akes place as indica ed in equa ions (9) and (10). As shown, inse ion is ollowed by a apid educ i e elimina ion which yields he co esponding o ganic and me allo-o ganic p oduc s. A di e en ia ion be ween he wo possible eac ion pa hways, namely inse ion in o he ni- ckel-alkyl o a yl ca bon bonds, can be accomplished by ca ying ou , in ei he o de , he sequen ial inse ions depic ed in eac ion (11) ( e . 18). Fo ma ion o 10 unequi ocally s ablishes ha he inse ion o CO akes place exclusi ely in o he nickel-ca bon alkyl bond. 9a B ough o you by | Biblio eca de la Uni e sidad de Se illa Au hen ica ed Download Da e | 9/10/19 10:14 AM Elec on ich me al complexes o CO, and CS, inco po a ion 1705 In he p esence o we C02, compound 9a unde goes a as p o oly ic clea age o he nickel- -a yl bond, wi h o ma ion o he binuclea , ca bona e-b idged species 11, eac ion (12). In he absence o wa e , he nickelalac one de i a i e 12 is o med as he esul o he inse - P PHCME CH 0 I 2 N~’ ‘C-O-N!-CH~C~~PH I (12) P Y p/ O’ 11 (13) NI 9a P’ o-c II 12 0 ion o ca bon dioxide in o he Ni-a yl bond ( eac ion 13). The exis ence in hese compounds o Ni-C bonds, sugges u he inse ion chemis y can be pu sued, and indeed, in e ac ion wi h ca bon monoxide (20°C, 1 a m) p oceeds as indica ed in eac ions (14) and (15). While he o me dese es no addi ional commen s, he esul s o he la e eac ion a e a he unexpec ed, ( e . 17) since hey co espond, in a o mal sense, o a me al p omo ed oxida i e conp opo iona ion o ca bona e and ca bonyl ligands. Two molecules o ca bon dioxide a e o med, one o hem is e ol ed as ee C02 and he o he becomes inco po a ed in o he anhy- d ide unc ionali y. The eac ion o 9a wi h 3-4 equi o ca bon disulphide ( e . 19) p oduces a ed-b own mic o- c ys alline p ecipi a e o he known complex 13 ( e . 20), oge he wi h a ed solu ion, om which ed c ys als o he di hiolac one 14 can be isola ed (Scheme 11). The na u e o 13 and 14 implies he in e mediacy o a Ni(0) species, 15, which can, in ac , be isola ed by he low empe a u e eac ion o 9a wi h a sligh de ec o ca bon disulphide. As expec ed, 15 eac s wi h excess CS2, wi h o ma ion o 13 and 14. I seems likely, ha he i s s ep in his eac ion is inse ion o ca bon disulphide in o he nickel-a yl ca bon bond, and his has been con i med, as al eady indica ed, by isola ion o complex 10, as he esul o he sequen ial inse ion o ca bon disulphide and ca bon monoxide (see eac ion 11). The esul- ing nickeladi hiolac one in e media e species, which would in ac be he CS2 analogue o 12, unde goes educ i e elimina ion, wi h concomi an in amolecula C-S bond o ma ion, o yield he obse ed complex 15. Scheme I/ B ough o you by | Biblio eca de la Uni e sidad de Se illa Au hen ica ed Download Da e | 9/10/19 10:14 AM 1706 E. CARMONA e a/. A e y di e en eac ion is obse ed be ween ca bon disulphide and complex 9b, he dmpe analogue o 9a. Upon addi ion o 2 equi o ca bon disulphide o a solu ion o 9b, he i hioca bona e 16 and he hioke ene 17 a e o med (Scheme 111). This eac ion co esponds o mally o a me al-induced educ i e disp opo iona ion o ca bon disulphide bu , a he in e es ingly, i occu s wi hou change in he oxida ion s a e o he me al cen e. Ac ion o 1 equi o ca bon disulphide upon compound 9b a o ds he 1,l-di hiola e species 18, which, as expec ed, eac s wi h ano he equi alen o ca bon disulphide, wi h o ma ion o 16 and 17. Thus, he cou se o he eac ion o ca bon disulphide wi h he nickelacyclopen ene de i a i- es 9 depends ma kedely on he na u e o he phosphine co-ligands. I seems easonable ha he eac ion o 9b wi h ca bon disulphide p oceeds also wi h ini ial inse ion o he he e o- cumulene in o he nickel-a yl bond. The chela ing na u e o he dmpe ligand p e en s phosphi- Scheme Ill 2 cs2 9b ne dissocia ion and may induce C-C ins ead o C-S bond o ma ion. Ne e heless, elec onic ac o s mus also play an impo an ole and his is clea ly mani es ed by he cou se o he eac ion o he 2,2'-bipy idine de i a i e 9c ( e . 18) wi h ca bon disulphide. As shown in equa ion (16), his yields a complex con aining he coo dina ed di hiolac one 14, ha is, a p oduc analogous o he ime hylphosphine de i a i e 15. No e idence o he o ma ion o a 1.1-di hiola e complex analogous o 18 has been ound. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19 * 20. 9c Acknowledgemen 1. The au ho s g a e ully acknowledge he con inuous suppo o he Minis e io de Educaci6n y Ciencia and he Agencia Nacional de E aluaci6n y P ospec i a. We hank P o esso Pie e B auns ein o a p e-p in o e e ence REFERENCES P. B auns ein, D. Ma and D. No el, Chem. Re . 88, 747 (1988) A. Beh ,,An ew. Chem. In . Ed. Engl. 27, 661 (1988). D. Wal he , Coo d. Chem. Re . 79, 135 (1987). D.J. Da ensbou g and R.A. Kuda oski, Ad . O gano ne . Chem. 22, 129 (1983). R.P.A. Sneeden, "Comp ehensi e O ganome allic Chemis y"; Pe gamon P ess: Ox o d 1982. C. Flo iani, Pu e & Appl. Chem. 54, 59 (1982). R. Al a ez, E. Ca mona, J.M. Ma in, M.L. Po eda, E. Gu ii ez-Puebla and A. 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