REACTIVITY OF PHOSPHINE PHOSPHINITE COMPLEXES - SYNTHESIS AND CRYSTAL-STRUCTURE OF [(PH2PCH=C(O)PH)PD(MU-PH2PO)]2

Treatment of cis-[MCl2{Ph2PCH = C(Ph)OPPh2}] (M = Pd, 1; Pt, 2) with 2 equivalents of KOH in dichloromethane yielded quantitatively the dinuclear complexes [M2{Ph2PCH = C(O)Ph}2{mu-(Ph2PO)}2] (M = Pd, 3; Pt, 4). The reaction of KOH with the nickel analogue of 1 led to dissociation of the phosphorus ligands and gave Ni(OH)2. The structure of 3.toluene was established by an X-ray diffraction study. Crystals of 3.toluene belong to the space group P1BAR with a = 12.76(1) angstrom, b = 14.672(5) angstrom, c = 18.657(9) angstrom, alpha = 76.97(3)-degrees, beta = 68.24(5)-degrees, gamma = 75.82(5)-degrees, V = 3110.1 angstrom-3, and Z = 2. The structure has been refined for 4254 reflections with F(o)2 > 3 sigma(F(o)2) to R = 0.033 and R(w) = 0.041. The structure consists of two square planar palladium centers linked together by two Ph2P-O bridges. The Pd-P(phosphine) bond length are 2.210(2) angstrom and 2.218(2)angstrom, and those of the Pd-(phosphinito) bonds 2.245(2) angstrom and 2.235(2) angstrom. The dihedral angle between the metal planes is 72.3-degrees (1) and the six-membered metal ring is in a boat conformation. The P-O bond lengths of 1.533(4) angstrom indicate some double bond character. Reaction of complex 1 with 2 equivalents of NaCo(CO)4 gave the trinuclear complex [{Ph2PCH = C(Ph)OPPh2}PtCo2(CO)7] (5). In contrast to 1 and 2, the complex 5 does not undergo hydrolytic cleavage of the phosphinite ligand, possibly for steric reasons. All the complexes were characterized by elemental analyses and IR, H-1 NMR, and P-31 NMR spectroscopy.