The synthesis and reactivity of electrophilic iridium(III) complexes containing bis(diphenylphospino) ethane

The complex Ir(CH3) (CO)(CF3SO3)(2)(dppe) (1) has been synthesized from the reaction of Ir(CH3)I-2(CO)(dppe) and silver triflate. Methane and IrH(CO)(CF3SO3)(2)(dppe) (2) are formed when a methylene chloride solution of 1 is placed under 760 torr dihydrogen. Conductivity studies indicate that methylene chloride solutions of complexes 1 and 2 are weak electrolytes and only partially ionized at concentrations above 1 mM. Complex 2 is an effective hydrogenation catalyst for ethylene and l-hexene while acetone hydrogenation is inhibited by the formation of [IrH2(HOCH(CH3)(2)) (GO) (dppe)] (OTf) (3). Linear dimerization and polymerization of styrene occurs via a carbocationic mechanism initiated by triflic acid elimination from 2. Treatment of an acetonitrile solution of Ir(CH3)I-2(CO)(dppe) with silver hexafluorophosphate produces the solvent promoted carbonyl insertion product [Ir(C(O)CH3)(NCCH3)(3)(dppe)] [PF6](2) (7) which readily undergoes deinsertion in methylene chloride to form [Ir(CH3)(CO) (NCCH3)(2)(dppe)] [PF6](2) (8) and acetonitrile.