Synthesis and solid-state structures of (triphos)iridacyclopentadiene complexes as models for vinylidene intermediates in the [2 + 2 + 1] cyclotrimerization of alkynes

The iridium 1,1,1-tris(diphenylphosphinomethyl)ethane (triphos) complexes [{κ2(C1,C4)-CRCRCRCR}{CH3C(CH2PPh2)3}Ir(NCMe)]BF4 (2-NCMe, R = CO2Me) and [{κ2(C1,C4)-CRCRCRCR}{CH3C(CH2PPh2)3}Ir(CO)]BF4 (2-CO, R = CO2Me) serve as models for proposed iridium–vinylidene intermediates of relevance to the [2 + 2 + 1] cyclotrimerization of alkynes. The solid-state structures of 2-NCMe, 2-CO, and [κ2(C1,C4)-CRCRCRCR]{CH3C(CH2PPh2)3}Ir(Cl) (2-Cl), were determined by X-ray crystallography.