Carborane reductive-elimination reaction from a six-coordinate hydridocarboranyliridium(III) complex: Kinetic and mechanistic study

A kinetic and mechanistic study of the reductive-elimination reaction of the carborane 1-H-T-C6H5-1,7-C2B10H10 (H-carb) from the six-coordinate iridium(III) complex Ir(H)(Cl)(σ-carb)(CO)(PPh3)2 has been carried out in 1,2-dichloroethane by IR spectroscopy between 20 and 50°C. The mechanism of the carborane-elimination reaction implies a preliminary PPh3 dissociation to give the five-coordinate Ir(H)(Cl)(σ-carb)(CO)(PPh3) complex. This intermediate then undergoes a reductive elimination of the carborane molecule through two pathways: (i) direct elimination to give the three-coordinate iridium(I) complex, IrCl(CO)(PPh3); (ii) a phosphine-induced elimination via trans → cis isomerization of the H and carb ligands. The kinetic and thermodynamic parameters are also reported and discussed. © 1984 American Chemical Society.