Synthesis and structure of platinum(II)- and palladium(II)-phosphorin complexes in solid and solution state

The novel platinum and palladium complexes with phosphorin, [Pt(dmppn)2X2] (X=Cl (1), Br (2), I (3)) and [Pd(dmppn)2X2] (X=Cl (4), Br (5)), have been prepared using 4,5-dimethyl-2-phenylphosphorin (dmppn) with M(cod)X2 or M(PhCN)2X2 (M=Pt, Pd). The crystal structure of 3 was determined by single crystal X-ray crystallography and shown a cis configuration in a square planar structure. The chemical shifts for these complexes were observed by 31P{1H} NMR spectroscopy in the solution and they showed significant upfield shifts over 30 ppm relative to that of the free ligand. These upfield shifts indicate that the phosphorin ligand undergoes strong π-back donation from the central metal compared with general phosphine ligands and the difference of these upfield shifts between Pt and Pd is clearly appeared the degree of π-back donation from the central metal. Molecular structure of platinum and palladium complexes in the solution was further estimated to have the cis configuration in the square planar with 31P{1H} and 13C{1H} NMR data.