Tungsten compounds octahedral clusters

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... 

Table IV lists specific examples of compounds related through this form of dimensional reduction, By far, the majority of these are zirconium chloride and iodide phases, in which case lower main group and even transition metals have been found to incorporate as interstitial atoms. A few analogues are known with hafnium (135), and very recently it has been shown that nitrogen can be substituted for carbon in tungsten chloride clusters adopting the centered trigonal-prismatic geometry (see Fig. 2) (32). It is hoped that a variability similar to that exposed for the octahedral zirconium clusters will be attainable for such trigonal-prismatic cluster phases.

---