Diverse Reactivity of Alkynes with the Binuclear Methyl and Incipient Methyl Complexes [RhIr(CH3)(CO)3(Ph2PCH2PPh2)2][CF3SO3] and [Ir2H(CO)3(μ-CH2)(Ph2PCH2PPh2)2][CF3SO3]

The binuclear diiridium complex, [Ir2H(CO)3(μ-CH2)(dppm)2][CF3SO3] (2), reacts with acetylene and phenylacetylene to give the alkyne- and vinylidene-bridged complexes, [Ir2(CH3)(CO)3(μ-HC⋮CR)(dppm)2][CF3SO3] and [Ir2(CH3)(CO)3(μ-CC(H)R)(dppm)2][CF3SO3] (R = H, Ph), respectively, in each case. At −78 °C in the acetylene reaction an intermediate acetylide−hydride, [Ir2(H)(CH3)(CO)3(μ-C⋮CH)(dppm)2)[CF3SO3], is observed, which transforms into the vinylidene product at higher temperature. The reaction of the related mixed-metal species [RhIr(CH3)(CO)3(dppm)2][CF3SO3] (1) with acetylene at −78 °C gives an acetylene-bridged intermediate analogous to that observed in the diiridium system, but warming to ambient temperature results in dissociation of the rhodium end of one of the diphosphines, which undergoes nucleophilic attack at the Rh end of the alkyne to yield [RhIr(CH3)(μ-η1:η2:η1-HCC(H)PPh2CH2PPh2)(dppm)][CF3SO3]. The reaction of 1 with phenylacetylene at −78 °C yields a methyl−hydrido−phenylacetylide inter...