Synthesis of a DMPM and Hydrido-Bridged Diiridium Complex, [(Cp*Ir)₂(μ-dmpm)(μ-H)₂][OTf]₂, and Its Reactivity toward Alkynes and Isocyanides

Reaction of [Cp*IrCl(muH)](2) (2) (Cp* = pentamethylcyclopentadienyl) with equimolar amounts of bis(dimethylphosphino)methane (dmpm) in THF followed by 2 equiv of AgOTf gives a new binuclear iridium complex, [(Cp*Ir)(2)(mu-dmpm)(mu-H)(2)] [OTf](2) (1). Complex 1 reacts with ethyne to give mu-vinyl complex, [(Cp*Ir)(2)(mu,eta(1),eta(2)-CH=CH2)(mu-dmpm)(mu-H)] [OTf](2) (4), via addition of the iridium hydride to the carbon-carbon triple bond. Reactions of 1 with terminal alkynes give mixtures of alpha-isomers of a mu-vinyl complex, [(Cp*Ir)(2)(mu,eta(1),eta(2)-CR=CH2)(mu-dmpm)(mu-H)][OTf](2) [R = Ph (5a), PhCH2 (5b), nBu (5c)], and -trans isomers [(Cp*Ir)(2)(mu,eta(1),eta(2)-CH=CHR)(mu-dmpm)(mu-H)][OTf](2) [R = Ph (6a), PhCH2 (6b), nBu (6c)]. The mu-vinyl ligand in 6a-c undergoes a fluxional process. Heating the alpha-isomers 5a-c at 120 degreesC results in isomerization to beta-trans isomers 6a-c. Complex 1 reacts with tert-butylisocyanide to give the simple adduct [(Cp*Ir)((CNBu)-Bu-t)(mu-dmpm)(mu-H)(Cp*Ir)(H)][OTf](2) (7), while reaction of 1 with phenylisocyanide or cyclohexylisocyanide gives mu-aminocarbyne complexes [(Cp*Ir)(2)-(mu,eta(1)-CN(H)R)(mu-dmpm)(mu-H)][OTf](2) [R = Ph (8a), Cy (8b)]. The structures of 1, 5c, 6a, 7, and 8a have been determined by X-ray diffraction methods.