Tungsten cluster compounds

Tungsten dichlofide [13470-12-7], WCI2, is an amorphous powder. It is a cluster compound and maybe prepared by the reduction of the hexachloride with aluminum in a sodium tetrachloroalurninate melt (11). 

A further point of interest is their ready interconversion in solution, which we have studied by variable temperature n.m.r. measurements (8). Reaction of [(n-C5H5)(0C)2W =CR] with polynuclear metal carbonyl species is likely to afford many new heteronuclear cluster compounds containing tungsten. 

Heterometal alkoxide precursors, for ceramics, 12, 60-61 Heterometal chalcogenides, synthesis, 12, 62 Heterometal cubanes, as metal-organic precursor, 12, 39 Heterometallic alkenes, with platinum, 8, 639 Heterometallic alkynes, with platinum, models, 8, 650 Heterometallic clusters as heterogeneous catalyst precursors, 12, 767 in homogeneous catalysis, 12, 761 with Ni—M and Ni-C cr-bonded complexes, 8, 115 Heterometallic complexes with arene chromium carbonyls, 5, 259 bridged chromium isonitriles, 5, 274 with cyclopentadienyl hydride niobium moieties, 5, 72 with ruthenium—osmium, overview, 6, 1045—1116 with tungsten carbonyls, 5, 702 Heterometallic dimers, palladium complexes, 8, 210 Heterometallic iron-containing compounds cluster compounds, 6, 331 dinuclear compounds, 6, 319 overview, 6, 319-352... 

Numerous trinuclear cluster compounds are formed by molybdenum, and to a lesser but significant extent by tungsten and niobium. Four principal types are known, and their structures are shown schematically in Fig. 16-22. In all of these the M—M bond orders are in the range % to 1. For molybdenum particularly, there are numerous mixed oxides in which the type of structure shown in Fig. 16-22(b) figures prominently. 

Molybdenum and tungsten in their lower oxidation states have a profound tendency to form M—M bonds, and therefore cluster compounds, as well as the dinuclear species just discussed in Section 18-C-10. One class of these clusters has already been presented in Sections 18-C-7 and 18-C-8, namely, the trinuclear species such as the M3Of+ and M3SJ+ cores and the cuboidal M4S3+ ones. This section will now deal with a number of other clusters of these elements. 

Cluster Compounds Inorganometallic Compounds Containing Transition Metal Main Group Elements Heterogeneous Catalysis by Metals Oxidation Catalysis by Transition Metal Complexes Polyoxometalates Tungsten Organometallic Chemistry. Tungsten Proteins. 

The chemical reduction of the higher Mo and W halides provides good yields of the octahedral clusters, but the mechanism is obscure. By contrast, chemical oxidation of zero-valent Mo and W leads to the bromo and iodo cluster species in poor yields but provides considerable insight into the formation of these cluster compounds. The reaction of the hexacarbonyls Mo(CO)6 or W(CO)6 with I2 at moderately low temperatures produces a mixture of metal halide phases (25, 16). In the reaction W(CO)6 with I2, lower nuclearity clusters have been isolated as reaction intermediates that lead to W6 species. The tri-, tetra-, and pentanuclear tungsten iodide species are obtained from W(CO)6 and I2 by varying reaction times and temperatures, and the... 

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