Synthesis and reactivity of five- and six-coordinate hydrido(vinyl) iridium(III) complexes

The reaction of the dihydrido indium(III) precursor [IrH2(Cl)(PiPr(3))(2)] (5) with internal alkynes RC equivalent to C(CO2Me) (R = Me, CO2Me) afforded the five-coordinate hydrido(vinyl) complexes [IrH(Cl){(E)-C(R)=CH(CO2Me)}(PiPr(3))(2)] (6, 7), via insertion of the alkyne into one of the Ir-H bonds. Compounds 6 and 7 are also accessible by careful hydrogenation of the alkyne iridium(I) derivatives trans-[IrCl{RC equivalent to C(CO2Me)}(PiPr(3))(2)] (9,10), the latter being prepared from in situ generated trans-[IrCl(C8H14)(PiPr(3))(2)] and RC equivalent to C(CO2Me). UV irradiation of 6 (R = CO2Me) led to the formation of the isomer [IrH(Cl){kappa(2)(C,O)-C(CO2Me)=CHC(OMe)=O}(PiP(3))(2)] (3) having the vinyl ligand coordinated in a bidentate fashion. While 6 reacted with acetonitrile and CO to afford the six-coordinate iridium(III) compounds [IrH(Cl){(E)-C(CO2Me)=CH(CO2Me)}(L')(PiPr(3))(2)] (11, 12), treatment of 6 with LiC5H5 gave the half-sandwich-type complex [(eta(5)-C5H5)IrH{(E)-C(CO2Me)=CH(CO2Me)}(PiPr(3))] (13) by, the loss of one PiPr(3). The reaction of 3 with CO under pressure resulted in the formation of [IrH(Cl){(Z)-C(CO2Me)=CH(CO2Me)}(CO)(PiPr(3))(2)] (14) in which, in contrast to the stereoisomer 12, the two CO2Me substituents are trans disposed. (c) 2006 Elsevier B.V. All rights reserved.