SYNTHESIS AND CHARACTERIZATION OF SOME BIMETALLIC PLATINUM-RHODIUM COMPLEXES - CRYSTAL-STRUCTURE OF [(PHCC)PT(MU-DPPM)2(MU-N2C3BR3)RH(CO)]PF6

The addition of pyrazolate ions to [ClPt(sigma,eta-C = CPh)(mu-dppm)2Rh(CO)]PF6 (dppm = bis(diphenylphosphino)methane) produces the complexes [(PhC = C)Pt(mu-Z)(mu-dppm)2Rh(CO)]PF6 (Z = Pyrazolate derivative). The use of the 3-methyl-5-trifluoromethylpyrazolate ion gives a mixture of the two isomers that contain the unsymmetrical pyrazolate ligand in its two possible orientations. The addition of t-BuNC to the complexes [(PhC = C)Pt(mu-Z)(mu-dppm)2Rh(CO)]PF6 leads to substitution of the CO by t-BuNC. The complexes [(CN)Pt(mu-Z)(mu-dppm)2Rh(CO)]PF6 were prepared in a similar manner from [(CN)2Pt(mu-dppm)2Rh(CO)Cl]. The dapm analogues [(CN)Pt(mu-35mpz)(mu-dapm)2Rh(L))]PF6 [dapm = (diphenylarsino)(diphenylphosphino)methane; 35mpz = 3,5-dimethylpyrazolate; L = CO, t-BuNC] and the complex [cis-ClPt(mu-35mpz)(mu-dapm)2-trans-Rh(CO)]PF6 have also been prepared and characterized. [(PhC = C)Pt(mu-345Bpz)(mu-dppm)2Rh(CO)]PF6 (345Bpz = 3,4,5-tribromopyrazolate) crystallizes in the triclinic space group P1BAR with a = 10.351(5), b = 14.707(6), c = 22.445(10) angstrom, alpha = 94.78(3)degrees, beta = 98.56(4)degrees, gamma = 107.68(3)degrees, V = 3189(2) angstrom 3 and Z = 2 at 298 K. The structure was refined to an R value of 0.0405 using 8382 unique reflections and 740 parameters. The structure consists of the platinum and rhodium atoms in square planar environments, each with two trans phosphorus atoms and a nitrogen atom from the pyrazolate ligand. The fourth ligand coordinated to the platinum atom is a terminal phenylacetylide ion and the fourth ligand coordinated to the rhodium atom is a terminal carbon monoxide.