SYNTHESIS OF UNSYMMETRICAL DPPM-BRIDGED PLATINUM AND PALLADIUM A-FRAME COMPLEXES

Reactions of [PtClR(cod)] (R = Me, Et, Ph) or [PtBr(Mes)(cod)] (Mes = mesityl) with 2 equiv of bis(diphenylphosphino)methane (dppm), followed by treatment with NH4PF6 or TIPF6, lead to complexes of the type [PtR(dppm-P,P')(dppm-P)]PF6, 1a-d, which contain one chelated and one dangling dppm ligand. The symmetrical, dppm-bridged complexes [Pt2R2(mu-Cl)(mu-dppm)2]PF6, 2a-c (R = Me, Et, Ph), are formed by treatment of [PtClR(cod)] with 1 equiv of dppm, followed by NH4PF6, and the unsymmetrical diplatinum A-frame complexes [Pt2RR'-(mu-Cl)(mu-dppM)2]PF6,2d-i, are formed by reactions of 1a-d with [PtClR'(cod)] (R' = Me, Et, Ph). The reaction of [PtMe(dppm-P,P')(dppm-P)]Cl with [PtBrMe(cod)] produces [Pt2M32(A-Br)(mu-dppm)2]Cl, which illustrates that it is the halide bound to platinum in the cyclooctadiene compound which ultimately occupies the bridging position in the A-frame product. The dipalladium complex [Pd2Me2(mu-Cl)(mu-dppm)2]PF6,2j, is prepared from [PdClMe(cod)], dppm, and NH4PF6, and the mixed metal complexes [PtPdRMe(mu-Cl)(mu-dppm)2]PF6, 2k-m (R = Me, Et, Ph), are obtained by addition of 1a-c to [PdClMe(cod)].