Regioselective permethylation, perallylation and perbenzylation of the arene ligand in [Ru(eta(5)-C5Me5)(eta(6)-C6Me6)][PF6]: a remarkable periodic effect

The reactions of [MCp*(eta(6)-C6Me6)][PF6], M = Fe: 1, Ru: 2, Cp* = eta(5)- C5Me5, with KOH (in DME) or tert-BuOK (in THF) and methyl iodide, allyl bro mide or benzyl bromide are regioselective on the arene ligand only for 2, g iving the complexes [RuCp*{eta(6)-C-6(CH2R)(6)}][PF6], R = methyl (3), ally l (4) or benzyl (5), although some formations of C-C bonds also occur on th e Cp* ligand in the case of the reactions of allyl and benzyl bromides. Thi s contrasts with the complete lack of regioselectivity formerly observed wi th the iron analogue I, and is best taken into account by the difference of steric effects which are less marked in 2 than in 1. (C) Academie des scie nces/Elsevier, Paris.