Hexa- and Octanuclear Heterometallic Clusters with Copper-, Silver-, or Gold-Molybdenum Bonds and d10-d10 Interactions

A comparative study of the reactivity of the carbonylmetalates {m}(-) = [MoCp(CO)(3)](-) (Cp = eta(5)-C-5-H-5) and [Mo(eta(5)-C5H4NMe2)(CO)(3)](-) toward d(10) complexes of the group 11 metals, [Cu(NCMe)(4)](BF4), AgBF4 and [N(n-Bu)(4)] [AuBr2], has allowed the characterization of new heterometallic hexa- and octanuclear clusters-with the same general formula [M{m}](n) (M = Cu, Ag, Au). In these cyclic oligomers, the value of n depends of the coinage metal. Thus, the hexanuclear cluster [Cu-3{Mo(eta(5)-C-5-H4NMe2)(CO)(3)}(3)] (17) has a planar metal core, formed by a copper triangle with edge-bridging molybdenum atoms. The-octanuclear "star shape" clusters [Ag-4{Mo(eta(5)-C-5-H4NMe2)(CO)(3)}(4)] (19) and [Au-4{Mo(eta(5)-C-5-H4NMe2)(CO)(3)}(4)] (21) contain a square silver or gold core, respectively, edge-bridged by molybdenum atoms. In these three clusters, the 2-D raft-type structure of their metal core, which is nu(2)-triangular for Cu3Mo3 and of a square-in-a-square-type for the octanuclear Ag4Mo4 and Au4Mo4 clusters, allows for d(10)-d(10) metallophilic interactions. The latter have been clearly evidenced by relatively short separations between the d(10) metal centers: average Cu center dot center dot center dot Cu, Ag center dot center dot center dot Ag, and Au center dot center dot center dot Au distances of 2.617(1), 2.869(1) and 2.792(1) angstrom, respectively. These new carbonyl clusters are closely related to their Cp analogs previously reported and constitute a unique set of heterometallic clusters with such geometries involving group 6 and group 11 transition metals.