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

Abstract

The reaction of the dihydrido iridium(III) precursor [IrH 2(Cl)(P iPr 3) 2] ( 5) with internal alkynes RC C(CO 2Me) (R = Me, CO 2Me) afforded the five-coordinate hydrido(vinyl) complexes [IrH(Cl){( E)-C(R) CH(CO 2Me)}(P iPr 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 C(CO 2Me)}(P iPr 3) 2] ( 9, 10), the latter being prepared from in situ generated trans-[IrCl(C 8H 14)(P iPr 3) 2] and RC C(CO 2Me). UV irradiation of 6 (R = CO 2Me) led to the formation of the isomer [IrH(Cl){κ 2( C, O)-C(CO 2Me) CHC(OMe) O}(P iPr 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(CO 2Me) CH(CO 2Me)}(L′)(P iPr 3) 2] ( 11, 12), treatment of 6 with LiC 5H 5 gave the half-sandwich-type complex [(η 5-C 5H 5)IrH{( E)-C(CO 2Me) CH(CO 2Me)}(P iPr 3)] ( 13) by, the loss of one P iPr 3. The reaction of 3 with CO under pressure resulted in the formation of [IrH(Cl){( Z)-C(CO 2Me) CH(CO 2Me)}(CO)(P iPr 3) 2] ( 14) in which, in contrast to the stereoisomer 12, the two CO 2Me substituents are trans disposed.