A series of hydrido(vinyl)iridium(III) complexes that are thermodynamically more stable than their olefin iridium(I) isomers

摘要

The reaction of the in situ generated cyclooctene iridium(l) derivative trans-[IrCI(C8H14)-(PiPr(3))(2)] with methyl vinyl ketone and other Michael systems RCH=C(R')C(O)R" (R = H, Me, Ph, OMe; R'= H, Me, iPr; R" = H, Me, OMe, NH2, NMe2) resulted in the formation of the octahedral hydrido(vinyl)iridium(III) complexes. [IrH(Cl){kappa(2)(C,O)-C(R)=C(R')C(R")=O}-(PiPr(3))(2)] (2-13) with the vinyl ligand coordinated in a bidentate fashion. Treatment of trans[IrCl(C8H14)(PiPr(3))(2)] with methyl acrylate and either dimethyl fumarate or dimethyl maleate afforded the iridium(I) compounds trans-[IrCI(eta(2)-RCH=CHCO2Me)(PiPr(3))(2)] (15, 16), which thermally or photochemically rearrange to the thermodynamically more stable iridium(III) isomers [IrH(CI){kappa(2)(C,O)-C(R)=CHC(OMe)=O}(PiPr(3))(2)] (17, 18) by intramolecular C-H activation. The reaction of trans- JrCK(8)H(14))(PiPr(3))(2)] with PhCH=CHC(O)Ph gave a 1:1 mixture of the isomeric iridium(III) complexes [IrH(Cl){kappa(2)(C,O)-C(Ph)=CHC(Ph)=O}(PiPr(3))(2)] (19) and [IrH(Cl){kappa(2)(C,O)-C6H4C(CH=CHPh)=O}(PiPr(3))(2)] (20), which were separated by column chromatography. From trans- [IrCK8H14)(PiPr(3))(2)] and acrylic acid both [IrH(Cl)-{kappa(2) (C,O)-CH=CHC(OH)=O}(PiPr(3))(2)] (21) and [IrH(Cl){kappa(2)(O,O)-O2CCH=CH2}(PiPr(3))(2)] (22) were obtained. While the attempted hydrogenation of [IrH2(Cl){kappa(2)(C,O)-CH=CHC(Me)=O}-(PiPr(3))(2) (2) with Pd/C as the catalyst led to the formation of [IrH2(Cl)(PiPr(3))(2)] (24) and ethyl methyl ketone, the same starting material reacted with a solution of C12 in chloroform to give the dichloro vinyl complex [IrCl2{kappa(2)(C,O)-CH=C(Cl)C(Me)=O}(PiPr(3))(2)] (27) in virtually quantitative yield. The reaction of both 2 and [IrH(I){kappa(2)(C,O)-CH=CHC(O)Me)=O}(PiPr(3))(2)] (29) with CO afforded the carbonyl compounds [IrH(X){eta(1)-(Z)-CH=CHC(O)Me}(CO)(PiPr(3))(2)] (31, 32) by partial opening of the chelate bond. Similarly to the Ir(PiPr(3))(2) counterparts, a series of (olefin)iridium(l) and hydrido(vinyl)iridium(III) compounds with Ir(PMetBu(2))(2) as a molecular unit were also prepared. Most remarkably, treatment of trans-[IrCl(eta(2)-CH2= CHC(O)H)(PMetBu(2))(2)] (43) with in situ generated trans-[IrCl(C8H14)(PMetBu(2))(2)] led to a clean cleavage of coordinated acrolein to CO and ethene and afforded a 1:1 mixture of trans[IrCl(CO)(PMetBu(2))(2)] (44) and trans- [IrCI(C2H4)(PMetBu(2))(2)] (45), respectively.