SYNTHESIS AND CHARACTERIZATION OF PLATINUM-GOLD CLUSTERS FUSED TO TETRAHEDRAL COPPER UNITS - CRYSTAL-STRUCTURES OF [PT(PPH(3))(AUPPH(3))(6)(CU(4)CL(3)PPH(3))](NO3) AND [PT(PPH(3))(AUPPH(3))(6)(CU4I3)](NO3)

Three new 11-metal-atom Pt-Au-Cu duster compounds are reported: [Pt(PP h(3))(AuPPh(3))(6)(Cu(4)Cl(3)PPh(3))]-(NO3) (1), [Pt(PPh(3))(AuPPh(3)) (6)(Cu4Br3(PPh(3))(y))](NO3) (2) (y = 0 or 1), and [Pt(PPh(3))(AuPPh(3 ))(6)(Cu4I3)](NO3) (3). These clusters are obtained from the reaction of [Pt(AuPPh(3))(8)](NO3)(2) with [PPh(3)CuX](4) (in which X = Cl, Br, or I, respectively). Cluster 1 was characterized by elemental analysi s, ICP analysis, FAB-MS, (variable-temperature) P-31 NMR and P-31 COSY spectroscopy, Pt-195 NMR spectroscopy, and IR spectroscopy. The cryst al and molecular structure of 1 has been determined by a single-crysta l X-ray analysis. The compound crystallizes as the NO3- salt in the tr iclinic space group <P(1)over bar> with Z = 2, a = 17.501(3) Angstrom, b = 21.152(6) Angstrom, c = 23.581(5) Angstrom, alpha = 92.18(2)degre es, beta 94.61(1)degrees, gamma = 109.69(2)degrees, and V = 8172 Angst rom(3). Mo K alpha radiation was used. The residuals are R = 0.068 and wR(2) = 0.162 for 11040 observed reflections and 788 variables. Clust er 3 was characterized by P-31 NMR spectroscopy and FAB-MS; its solid- state structure was determined by means of a single-crystal X-ray anal ysis. This duster compound crystallizes as the NO3- salt in the monocl inic space group P2(1)/c, with Z = 4, a = 17.871(4) Angstrom, b = 34.6 87(3) Angstrom, c = 23.357(2) Angstrom, beta = 95.49(2)degrees, and V = 14412 Angstrom(3). Mo K alpha radiation was used. The residuals are R = 0.117 and wR(2) = 0.285 for 2957 observed reflections and 340 vari ables. Both clusters, 1 and 3, have a tetrahedral Cu-4 unit which is f ace (eta(3)) bonded to the (central) platinum atom, which is furthermo re surrounded by six gold atoms. Short copper-gold and copper-platinum distances show that the copper atoms, although coagulated, are part o f the metal cluster core. In cluster 1 an additional PPh(3) ligand is present on the Cu-4 unit as compared to 3; in solution this copper-bon ded phosphine of 1 is shown to dissociate reversibly. The cluster comp ound 2 was characterized by means of P-31 NMR spectroscopy, which indi cates this cluster to be analogous to clusters 1 and 3.