Activation of CH bonds by transition metals : V. A study of the mechanism of metallation reactions of benzyl- and meta-fluorobenzylphosphines with Rh I, Ir I, Pd II and Pt II compounds

Abstract

Reaction of R 2PCH 2C 6H 5 (R = cyclohexyl or t-butyl) with [(COT) 2RhCl] 2, [(COT) 2IrCl] 2, PdCl 2 or PtCl 2(benzonitrile) 2 yields cyclometallated compounds. The reactivity appears to decrease in the order Ir I ρ Rh I ρ ρ Pd II ≈ Pt II, suggesting a different reaction mechanism for univalent and bivalent d 8 metal atoms. Reaction of meta-FC 6H 4CH 2PR 2 with the same metal chlorides shows that for Rh I and Ir I a nucleophilic mechanism operates and for Pd II an electrophilic one. For Pt II no decision could be made on the basis of these experiments. Steric effects have a large influence on the rates of the reactions.