C−H Bond Activation and Subsequent C(sp2)−C(sp3) Bond Formation: Coupling of Bromomethyl and Triphenylphosphine in an Iridium Complex.

Treatment of HCCCH(OH)CHCH2with [IrHCl(CO)(PPh3)3]BF4at room temperature afforded an iridacyclohexadiene, [Ir(CHC(PPh3)CHCHCH2)Cl(CO)(PPh3)2]BF4(1). The reactivity of complex 1had been investigated. Reaction of 1with 1 equiv of bromine produced an iridacyclopentadiene, [Ir(CHC(PPh3)CHC(CH2Br))Cl(CO)(PPh3)2]BF4(2). When excess bromine was used, iridacyclopentadiene 2underwent subsequent intramolecular C(sp2)−C(sp3) coupling between the exocyclic −CH2Br group and a phenyl of the PPh3ligand, leading to the formation of a fused iridacycle complex, [Ir(CHC(PPh3)C(Br)C(CHBr))(P(C6H4)Ph2)Cl(CO)PPh3]Br3(3). A mechanism for the formation of complex 3starting from 1was proposed, in which the process involved a triple C−H activation as well as a rare C(sp2)−C(sp3) reductive elimination. [ABSTRACT FROM AUTHOR]