Reactions of co-ordinated ligands. Part IX. Insertion reactions of π-allylic iridium(I) complexes with hexafluorobut-2-yne

Abstract

Reaction of hexafluorobut-2-yne (HFB) with [Ir(π-allyl)(CO)PPh₃)₂](π-allyl = C₃H₅ or 2-MeC₃H₄) in toluene solution affords the cis-insertion products [[graphic omitted]CH₂(CO)_x(PPh₃)_y](x= 1, y= 2; x= 2, y= 1; R = H or Me) together with the trans-insertion 1 : 1 adduct [Ir{C(CF₃)[graphic omitted]C(CF₃)CH₂·CRCH₂}(CO)(PPh₃)₂]. When the reaction is carried out in a solvent mixture of toluene–methanol the complexes [[graphic omitted]C(CF₃)(π-allyl)(CO)(PPh₃)] are formed, the 2-methylallyl complex being transformed into a mixture of the cis- and trans-insertion products on treatment with triphenylphosphine. In toluene at –30 °C, [Ir(π-1-MeC₃H₄)(CO)(PPh₃)] reacts with HFB to give a very low yield of a trans-insertion product, whereas from a prolonged reaction in benzene the complexes [Ir{C(CF₃)C(CF₃)H}(1–4η-C₄H₆)(CO)(PPh₃] and [[graphic omitted](CF₃)(π-1-MeC₃H₄)(CO)(PPh₃)] were obtained. The corresponding reaction of [Ir(2-MeC₃H₄)(CO)(diphos)] affords a cis-insertion product together with the complex [(CF₃)[graphic omitted]CH₂}(CO)(diphos)]. The n.m.r. spectra of the complexes and possible mechanisms for their formation are discussed.