NOVEL REACTIONS OF METAL-METAL BONDS - ADDITION OF SULFUR-DIOXIDE AND SULFUR TO PD2(PH2PCH2PPH2)2CL2 AND THE OXIDATION OF COORDINATED SULFIDE

Sulfur dioxide inserts into the metal-metal bond of Pd2(dpm)2X2 (dpm = bis(diphenylphosphino)methane, X = CI or Br), Pd2(dam)2Cl2 (dam = bis(diphenylarsino)methane), and Pt2(dpm)2Cl2. The adducts have been crystallized and characterized by infrared, electronic, and 1H NMR spectroscopy. The structure of Pd2(dpm)2(μ-SO2)Cl2 has been determined by X-ray crystallography. The compound crystallizes in the orthorhombic space group P212121 with four molecules per unit cell of dimensions a = 15.582 (3), b = 16.457 (3), and c = 19.184 (5) Å. Full-matrix least-squares refinement yields R = 0.069. The binuclear molecules contain two approximately planar palladium ions, each coordinated to a terminal chloride, a bridging sulfur dioxide, and two trans phosphorus donors from the bridging diphosphines. The ability of crystal packing forces to alter the Pd⋯Pd separation (3.383 (4) and 3.220 (4) Å for the two crystallographically independent molecules) reflects the lack of a direct metal-metal bond. Pd2(dpm)2Cl2 reacts with cyclo-octasulfur or propylene sulfide to give Pd2(dpm)2(μ-S)Cl2, which has been crystallized and characterized by infrared, electronic, and 1H NMR spectra. An X-ray structure determination reveals that Pd2(dpm)2(μ-S)Cl2 has a geometry nearly identical with that of Pd2(dpm)2(μ-SO2)Cl2. Crystals of Pd2(dpm)2(μ-S)Cl2 are tetragonal, space group with Z = 4 and cell dimensions a = 21.015 (4) and c = 14.281 (2) Å. Refinement of this complex yields an R of 0.076. Oxidation of Pd2(dpm)2(μ-S)Cl2 with m-chloroperbenzoic acid has been monitored by electronic spectroscopy at -60 °C; Pd2(dpm)2(M-SO2)Cl2 is formed. The utility of the 1H NMR spectra of the methylene region of these dpm-bridged complexes in diagnosing the structure of the complexes is discussed. © 1979, American Chemical Society. All rights reserved.