1,1' BIS(DIPHENYLPHOSPHINO)FERROCENE COMPLEXES OF PLATINUM(II) AND PLATINUM(I) - CRYSTAL AND MOLECULAR-STRUCTURE OF [(FE(ETA-5-C5H4PPH2)PT(MU-H)(MU-CO)PT(FE(ETA-5-C5H4PPH2)2)][BF4]-0.5H2O