Factors affecting the lability of the σ(M-X) bond in cycloplatinated and cyclopalladated complexes containing [C(sp2, ferrocene),N,X]- or [C(sp2, phenyl),N,X]-(X = S, N) terdentate ligands

The reactions of the cyclometallated complexes [M {[(n(5)-C5H3)-CH=N-(C6H4-2-SMe)]Fe(n(5)-C5H5)}Cl] [with M = Pt (5a) or Pd (5b)] with PPh3 under different experimental conditions are reported.These studies have allowed the isolation of [M{[(eta(5)- C5H3)-CH=N-C6H4-2-SMe]Fe(eta(5)-C5H5)}(PPh3)]X [M = Pt and X- = Cl- (6a) or BF4- (7a) or M = Pd and X- = Cl- (6b) or BF4- (7b)] and the neutral complex [Pd{[eta(5)-C5H3)-CH=N-(C6H4-2-SMe)]Fe(eta(5)-C5H5)}Cl(PPh3)] (8b). In 6-7a,b the ferrocenyl Schiff base behaves as a [C(sp(2), ferrocene),N,S](-) group while in 8b it acts as a [C(SP2, ferrocene),N](-) ligand. The X-ray crystal structure of 7b confirms the mode of binding of the ferrocenyl ligand.The comparison of the results obtained and those reported for [M{(C6H4)-CH=N-(CH2-CH2-2-SEt)}Cl] and [M{(C6H4)-CH=N-(C6H4-2-SMe)Cl] {with a [C(SP2, phenyl),N,S](-) terdentate ligand} or [M{eta(5)-C5H3)-CH=N-(CH2)(3)-NMe2]Fe(eta(5)-C5H5)}Cl] {in which the ligand acts as a [C(sp(2), ferrocene),N,N'](-) group} have allowed the elucidation of the relative importance of the factors affecting the lability of the M-X (X = S or N') and M-Cl bonds in cyclometallated compounds with [C,N,S](-) and [C(sp(2), ferrocene),N,X](-) ligands. (C) 2004 Elsevier B.V. All rights reserved.