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

The 3-phenyl-2-(pyridin-2-yl)oxazolidine ligand (ppo) was synthesized and its coordination behavior regarding Ni(II) and Pd(II) centers was studied. The reaction with K2PdCl4 affords [Pd(N,N'-ppo)Cl2] (1), in which ppo chelates to Pd via the pyridyl-nitrogen and the oxazolyl nitrogen atoms. The reaction of ppo with NiCl2·6H2O produces [Ni(N,O-ppo)2Cl2] (2), in which two ppo ligands are coordinated via the pyridyl-nitrogen and the oxygen atom of the oxazolidine ring. The x-ray diffraction anal. of the complexes confirms a square planar geometry for Pd(II) in 1 and an octahedral configuration around Ni(II) in 2, which, to the best of the authors' knowledge, represents the first reported example of a structurally characterized nickel-oxazolidine compd. Both complexes prove to be active catalysts under mild conditions in the aza-Michael reaction of (E)-4-phenylbut-3-en-2-one (benzalacetone) with aliph. amines. [on SciFinder(R)]