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 [CpFeη5C5H4–CH=N–CH2n–C4H3S] Cp = η5C5H5 and n= 1 1b or 2 1c with Na2[PdCl4] and NaAcO·3H2O gave [CpFeμη5Feη1PdC5H3–CH=N–CH2n–C4H3SCl] n= 1 2b or 2 2c with a [Csp2,ferrocene,N,Sthienyl]–ligand. The study of the reactivity of 2bor 2cwith PPh3under different experimental conditions has afforded the isolation of [CpFeμη5Feη1PdC5H3–CH=N–CH2n–C4H3SClPPh3] n= 1 3b or 2 3c and[CpFeμη5Feη1PdC5H3–CH=N–CH2n–C4H3SPPh3][BF4] n= 1 4b or 2 4c where 1bor 1cbehave as a bidentate [Csp2,ferrocene,N]–in 3band 3c or as a terdentate [Csp2,ferrocene,N,Sthienyl]–in 4band 4c ligand. The crystal structures of 3b·12CH2Cl2, 3c·2H2O and 4c·CH2Cl2confirm the mode of binding of the ligands. The results obtained from these studies and the solution behaviour of 4band 4creveal that the σPd–S bond of 2b, 2c, 4band 4cis more labile that in [CpFeμη5Feη1PdC5H3–CH=N–C6H42SMeCl] or [CpFeμη5Feη1PdC5H3–CH=N–C6H42SMePPh3][BF4] with a [Csp2,ferrocene,N,Sthioether]–ligand.