Group 6 metal halide clusters

The most convenient route to M6Yi2F clusters of niobium and tantalum is the conproportionation of the pentahalides NbYs and TaYs (Y = Cl, Br) with excess of the metal in molten alkali halide  

Initial studies on the redox properties of the M6Yi2 clusters were reported on poorly defined complexes simply noted as [TaeCli2] or [Nb(jCli2] (122). Aqueous cluster solutions were prepared from the sulfate salts TaeCli2S04 and Nb6Cli2S04 with various electrolytes. Some combination of water molecules and anions fills the coordination sphere of the MeY cluster. Despite these ambiguities, the oxidized compounds M6Yi2 were obtained with various chemical oxidants by a two-electron transfer process (123)  

Subsequent investigations (124-126) revealed an equilibrium between the intermediate Mi Yi2F state and the MeYi2P and M6Yi2 clusters. 

Cyclic voltammetry studies (127) on Ta6Bri2 reveal two reversible one-electron oxidations corresponding to generation of the n = 3 and n = 4 states, 

The hydrated complexes M6Yi2Y2(H20)4-4H20 (MgYn) provide more versatile precursors to new M6Yi2F (M = Nb, Ta) derivatives. The 

In basic solutions the M6Yi2 2+ core is rapidly oxidized upon exposure to air. Presumably the strong a- and 77-donor properties of hydroxide and alkoxide ligands increase electron density on the 

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Early transition metal halide clusters, see Group 5 metal halide clusters Group 6 metal halide clusters... 

Redox Chemistry and Photophysics of the Group 6 Metal Halide Clusters Molecular and Electronic Structure of the Group 6 Metal Halid Clusters Group 5 Metal Halide Clusters A. Synthesis of Cluster Core... 

D. Redox Chemistry and Photophysics of the Group 6 Metal Halide Clusters... 

Early synthetic procedures for the group 6 metal halide clusters relied on disproportionation reactions of the intermediate halides, MoC13, MoBr3, WC14, and WBr4, at elevated temperatures to produce the clusters MgX (11, 12). These reactions suffered from inherently poor yields and the need to synthesize and isolate the reactive intermediate metal halide. McCarley and co-workers (13) introduced the use of sodium tetrahaloaluminate melts to reduce the halides MoX5 and WX (X = Cl, Br) with aluminum at lower temperatures ... 

Redox Chemistry of the Group 5 Clusters Ligand Substitution Electronic and Molecular Structure Niobium Iodide Clusters NbJJ"-Materials Chemistry Derived from Soluble Metal Halide Clusters A. Higher Nuclearity Clusters Supported Cluster Materials Charge-Transfer Salt Complexes Extended Solids Chemically Modified Surfaces... 

A review28 describes compounds of the Pt-group metals including halide, oxide, sulfide, coordination compounds, organometallic compounds, and metal cluster compounds. 

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