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{[(η5-C5H3)–CHdouble bond; length as m-dashN–(C6H4–2-SMe)]Fe(η5-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{[(η5-C5H3)–CHdouble bond; length as m-dashN–C6H4–2-SMe]Fe(η5-C5H5)}(PPh3)]X [M = Pt and X− = Cl− (6a) or View the MathML sourceBF4- (7a) or M = Pd and X− = Cl− (6b) or View the MathML sourceBF4- (7b)] and the neutral complex [Pd{[(η5-C5H3)–CHdouble bond; length as m-dashN–(C6H4–2-SMe)]Fe(η5-C5H5)}Cl(PPh3)] (8b). In 6–7a,b the ferrocenyl Schiff base behaves as a [C(sp2, 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)–CHdouble bond; length as m-dashN–(CH2–CH2–2-SEt)}Cl] and [M{(C6H4)–CHdouble bond; length as m-dashN–(C6H4–2-SMe)}Cl] {with a [C(sp2, phenyl),N,S]− terdentate ligand} or [M{[(η5-C5H3)–CHdouble bond; length as m-dashN–(CH2)3–NMe2]Fe(η5-C5H5)}Cl] {in which the ligand acts as a [C(sp2, 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(sp2, ferrocene),N,X]− ligands.