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=CH2, with [IrHCl(CO)(PPh3)(3)]BF4 at room temperature afforded an iridacyclohexadiene, [Ir(CH=C(PPh3)CH=CHCH2)Cl(CO)(PPh3)(2)]BF4 (1). The reactivity of complex 1 had been investigated. Reaction of 1 with 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 2 underwent subsequent intramolecular C(sp(2))-C(sp(3)) coupling between the exocyclic-CH2Br group and a phenyl of the PPh3 ligand, leading to the formation of a fused iridacycle complex, [Ir(CH=C(PPh3)C(Br)=C(CHBr))(P(C6H4)Ph-2)Cl(CO)PPh3]Br-3 (3). A mechanism for the formation of complex 3 starting; from 1 was proposed, in which the process involved a triple C-H activation as well as a rare C(sp(2))-C(sp(3)) reductive elimination.