Study on the Lability of the σ(Pd-S) Bond of Novel Palladacycles with [C(sp2,ferrocene),N,S(thienyl)]- Pincer Ligands

The reaction of [(Cp)Fe{(eta(5)-C5H4)-CH=N-(CH2)(n)-(C4H3S)}] {Cp = (eta(5)-C5H5) and n = 1 (1b) or 2 (1c)) with Na-2[PdCl4] and NaAcO center dot 3H(2)O gave [(Cp)Fe{(mu-eta(5)-Fe-eta(1)-Pd-C5H3)-CH=N-(CH2)(n)-(C4H3S)}Cl] {n = 1 (2b) or 2 (2c)} with a [C(sp(2),ferrocene),N,S(thienyl)](-) ligand. The study of the reactivity of 2b or 2c with PPh3 under different experimental conditions has afforded the isolation of [(Cp)Fe{(mu-eta(5)-Fe-eta(1)-Pd-C5H3)CH=N-(CH2)(n)-(C4H3S)}Cl(PPh3) {n = 1 (3b) or 2 (3c)} and [(CP)Fe{(mu-eta(5)-Fe-eta(1)-Pd-C5H3)-CH=N-(CH2)n-(C4H3S)}- (PPh3)][BF4] {n = 1 (4b) or 2 (4c)} where 1b or 1c behave as a bidentate [C(sp(2),ferrocene),N](-) (in 3b and 3c) or as a terdentate [C(sp(2),ferrocene),N,S(thienyl)](-) (in 4b and 4c) ligand. The crystal structures of 3b center dot 1/2CH(2)Cl(2), 3c center dot 2H(2)O and 4c center dot CH2Cl2 confirm the mode of binding of the ligands. The results obtained from these studies and the solution behaviour of 4b and 4c reveal that the sigma(Pd-S) bond of 2b, 2c, 4b and 4c is more labile that in [(Cp)Fe{(mu-eta(5)-Fe-eta(1)-Pd-C5H3)-CH=N-(C6H4-2SMe))Cl] or [(CP)Fe{(mu-eta(5)-Fe-eta(1)-Pd-C5H3)-CH=N-(C6H4-2SMe))(PPh3)][BF4] with a [C(sp(2),ferrocene),N,S-(thioether)](-) ligand.