Ni(II) and Pd(II) pyridinyloxazolidine-compounds: synthesis, X-ray characterisation and catalytic tests in the aza-Michael reaction

The 3-phenyl-2-(pyridin-2-yl)oxazolidine ligand (ppo) was synthesised and its coordination behaviour regarding to Ni(II) and Pd(II) centres studied. The reaction with K2PdCl4 afforded compound [Pd(N,N’-ppo)Cl2] (1), where ppo binds to palladium via the nitrogen on the pyridine and the nitrogen on the oxazolidine moiety. On the contrary, by reaction with NiCl2·6H2O, the [Ni(N,O-ppo)2Cl2] species, (2), was obtained, having the ligand coordinated via the pyridine nitrogen and the oxygen of the oxazolidine ring. The discussed complexes proved to be active catalysts in the aza-Michael reaction of (E)-4-phenylbut-3-en-2-one (benzalacetone) with aliphatic amines, in mild conditions.