ACTIVATION OF C-H BONDS BY TRANSITION-METALS .5. STUDY OF THE MECHANISM OF METALATION REACTIONS OF BENZYLPHOSPHINES AND META-FLUOROBENZYLPHOSPHINES WITH RHI, IRI, PDII AND PTII COMPOUNDS

Reaction of R2PCH2C6H5 (R = cyclohexyl or t-butyl) with [(COT)2RhCl]2, [(COT)2IrCl]2, PdCl2 or PtCl2(benzonitrile)2 yields cyclometallated compounds. The reactivity appears to decrease in the order IrI ρ RhI ρ ρ PdII ≈ PtII, suggesting a different reaction mechanism for univalent and bivalent d8 metal atoms. Reaction of meta-FC6H4CH2PR2 with the same metal chlorides shows that for RhI and IrI a nucleophilic mechanism operates and for PdII an electrophilic one. For PtII no decision could be made on the basis of these experiments. Steric effects have a large influence on the rates of the reactions. © 1979.