THE HETERONUCLEAR CLUSTER CHEMISTRY OF THE GROUP-1B METALS .15. EFFECT OF THE NATURE OF THE GROUP-1B METALS AND THE CONE ANGLES OF THE ATTACHED PHOSPHINE-LIGANDS ON THE METAL FRAMEWORK STRUCTURES OF HETERONUCLEAR CLUSTER COMPOUNDS - SYNTHESIS, STRUCTURES, AND DYNAMIC BEHAVIOR OF THE BIMETALLIC HEXANUCLEAR CLUSTER COMPOUNDS [M2RU4H2(CO)12(PR3)2] (M = CU, R = CHME2 OR C6H11 - M = AG OR AU, R = CHME2, C6H11, OR CME3)

Treatment of the salt [N(PPh3)2]2[Ru4(mu-H)2(CO)12] with 2 equivalents of the complex [M(NCMe)4]PF6 at - 30-degrees-C, followed by the addition of 2 equivalents of PR3, affords the hexanuclear cluster compounds [M2Ru4(mu3-H)2(CO)12(PR3)2] [M = Cu, R = CHMe2, or C6H11 (C6H11 = cyclohexyl); M = Ag, R = CHMe2, C6H11, or CMe3] in ca. 50-65% yield. The analogous gold-containing species [Au2Ru4H2(CO)12(PR3)2] (R = CHMe2, C6H11, or CMe3) were prepared in ca. 30-50% yield from the reaction of [N(PPh3)2]2[Ru4(mu-H)2(CO)12] with 2 equivalents of the compound [AuCl(PR3)], in the presence of TIPF6. Despite the relatively large size of the P(C6H11)3 ligand, the clusters [M2Ru4H2(CO)12{P(C6H11)3}2] (M = Ag or Au) still adopt the capped trigonal-bipyramidal skeletal geometry, with the Group 1B metals in close contact, which previous work has shown is preferred by clusters of general formula [M2Ru4H2(CO)12 L2] (M = Cu, Ag, or Au) when L is a smaller monodentate phosphine or phosphite ligand. However, the smaller size of the copper atom relative to silver and gold means that the P (C6H11)3 ligand is too bulky to allow two adjacent Cu{P(C6H11)3} fragements to be accommodated in the metal framework of [Cu2Ru4(mu-3-H)2-(CO)12{P(C6H11)3}2]. Thus, the cluster is forced to adopt a sterically less-demanding skeletal geometry, which consists of a Ru4 tetrahedron with one edge bridged by a Cu{P(C6H11)3} unit and a non-adjacent face capped by the second such group. When the phosphine ligand P (CMe3)3, which is larger than P (C6H11)3, is attached to the Group 1B metals in the clusters [M2Ru4(mu-3-H)2-(CO)12{P(CMe3)3}2] (M = Ag or Au), the silver- and gold-containing species are also forced to adopt a similar sterically less-demanding edge-bridged trigonal -bipyramidal metal core structure. In addition, the P(CMe3)3 ligand seems to be too bulky to allow a hexanuclear cluster of formula [Cu2Ru4H2(CO)12{P(CMe3)3}2] even to adopt an edge-bridged trigonal -bipyramidal metal framework structure and an attempt to prepare this species afforded the pentanuclear cluster [CuRu4(mu-3-H)3-(CO)12{P(CMe3)3}] instead. The phosphine ligand P(CHMe2)3, which is smaller than P(C6H11)3, is not sufficiently bulky to cause the metal cores of [M2Ru4(mu3-H)2(CO)12{P(CHMe2)3}2] (M = Cu, Ag, or Au) to change from the preferred capped trigonal-bipyramidal skeletal geometry in the solid state, but a second isomer of the copper-containing cluster, which probably has two face-capping Cu{P(CHMe2)3} units with no bonding interaction between them, is also present in solution at low temperatures. Variable-temperature 31P-{H-1} and H-1 n.m.r. spectroscopic studies demonstrate that the new Group 1B metal heteronuclear cluster compounds undergo a variety of interesting dynamic processes in solution.