Palladium complexes with hydrophosphorane ligands (HP∼O and HP∼N), catalysts for Heck cross-coupling reactions

The synthesis and structural characterization of palladium complexes 1–3 incorporating H-spirophosphorane HP(OCMe2CMe2O)2 and H-phosphonate congener HP(O)(OCMe2CMe2O) ligands are reported. The chemical composition of the complexes [PdCl(μ-Cl){P(OCMe2CMe2O)OCMe2CMe2OH}]2 (1), [Pd{P(O)(OCMe2CMe2O)}2]n (2), and [Pd(μ-Cl){P(OCMe2CMe2O)OH}{P(OCMe2CMe2O)O}]2 (3) was established by means of NMR, IR, ESI-MS spectroscopic methods. The relative stereochemistry of 1 and 3 was unambiguously determined by single X-ray diffraction studies. It was proved that complexes 1–3, and complex [PdCl2P(OCH2CMe2NH)OCH2CMe2NH2] (4) previously described in the literature, are very efficient catalysts for the Heck cross-coupling of bromobenzene with n-butyl acrylate. Moreover, they were also found to be effective catalysts in the stereoselective synthesis of trans-stilbenes.