Iridium Complexes Containing Four and Five Ir−C Bonds: Alkyl-Bis(alkenyl)-Alkynyl and Carbonyl-Alkyl-Bis(alkenyl)-Alkynyl Iridium

Iridium complexes containing four Ir−C σ-bonds, cis, cis -[Ir(CH 3 )(−CH CHPPh 3 ) 2 (−C⋮CR)(PPh 3 ) 2 ] + ( 2, R = p -C 6 H 4 CH 3 ( a ), cyclohex-1-enyl ( b ), C(CH 3 ) CH 2 ( c )), are obtained from the reactions of cis, trans -[Ir(CH 3 )(−CH CHPPh 3 ) 2 (CO)(PPh 3 ) 2 ] 2+ ( 1 ) with HC⋮CR in the presence of Me 3 NO. One of the two PPh 3 in 2 is readily replaced to give complexes containing five Ir−C σ-bonds, cis -[Ir(CO)(CH 3 )(−CH CHPPh 3 ) 2 (−C⋮CR)(PPh 3 )] + ( 3, R = p -C 6 H 4 CH 3 ( a ), cyclohex-1-enyl ( b ), C(CH 3 ) CH 2 ( c )). Complexes 3 are also obtained from the reactions of 2 with CHCl 3 in the presence of OH - in H 2 O. The reaction of trans- [IrBr(CH 3 )(−CH CHPPh 3 ) 2 (CO)(PPh 3 )] + ( 4 ) with Ag + and 4-ethynyltoluene in the presence of NEt 3 gives a mixture of geometric isomers, 3a (where the CH 3 group is cis to −C⋮C- p -C 6 H 4 CH 3 ligand) and 3 ‘ a (where the CH 3 group is trans to −C⋮C- p -C 6 H 4 CH 3 ligand). Addition of aqueous HCl to 2a or 3a causes a new carbon−carbon bond formation between the methyl and alkynyl groups to produce cis- CH 3 CH CH- p -C 6 H 4 CH 3 ( 5 ) exclusively and [IrCl 2 (−CH CHPPh 3 ) 2 (PPh 3 )(L)] + (L = PPh 3, CO).