SYNTHESIS AND CHARACTERIZATION OF 5-COORDINATE OLEFIN COMPLEXES OF PALLADIUM(II) - MOLECULAR-STRUCTURE OF THE ACETONE SOLVATE OF (2,9-DIMETHYL-1,10-PHENANTHROLINE)(MALEIC ANHYDRIDE)METHYLCHLOROPALLADIUM

Five-coordinate olefin complexes of palladium(II) of general formula PdClMe(N-Nʹ) (η2-olefin) have been prepared by reaction of the dimeric complex [PdClMe(Me2S)]2 with planar sterically crowded nitrogenous bidentate ligands and the appropriate olefin. The X-ray crystal structure of the complex having N-Nʹ = 2,9-dimethyl-1,10-phenanthroline and olefin = maleic anhydride has been determined. This crystallizes in the monoclinic system, space group P21/n, with a = 7.085 (2) Å, b = 15.880 Å, c = 19.062 Å, β= 96.79 (5)°, and Z = 4. Refinement converged at R = 0.024 (Rw = 0.026), and the geometry of the five-coordinate palladium is trigonal bipyramidal, with the olefinic double bond in the equatorial plane and the chloride and methyl ligands in apical positions. The stability and structural and NMR spectroscopic properties of the complexes are discussed in comparison with those of analogous Pt(II) derivatives and point to a relevant contribution of π-back-donation to the Pd‒olefin bond in the five-coordinate species. © 1990, American Chemical Society. All rights reserved.