Chalcogen molybdenum

Fig. 6.1 The fundamental structural unit found in the Chevrel phases (cluster MoeXg full circles Mo atoms) displayed in three ways to emphasize different views of the connectivity. In (a) an octahedron of molybdenums (Mo-Mo = 2.7 A) is encased in a cube of chalcogens (Mo-S 2.45 or Mo-Se 2.6 A). Scheme (b) exhibits the same cluster as consisting of an octahedron with its triangular faces capped by chalcogenides. In (c), the cluster has been reoriented so that a threefold axis is vertical. (Reproduced from [10])...

In order to make these points clearer, interatomic distances in representative compounds are listed in Table VII. The distortion of Mo6 should be caused by electronic effects from the individual cluster units and/or steric effects due to the linkage of the clusters. At one time the electronic effects were considered more important based on the band calculations (58, 84). The strong eg Mo rf-bonding character of the conduction band causes contraction of the Mo octahedron, and the filling of the tlu(Oh) - eu (S6) and t2u (Oh) —> au (S6) band is related to the smaller intratriangle distance. Namely, the larger shift of electrons from Mx and chalcogen atoms to the molybdenum atoms is related to smaller distortion of the Mo6 octahedra. 

Molybdenum coordination has recently been comprehensively reviewed in Comprehensive Coordination Chemistry, particularly in the areas of mononuclear complexes, polyoxometaUate synthesis, structure, and reactivity see also Polyoxometalates), and in chalcogen-containing cluster complexes. ... 

Since both BF3 or SbFs form adducts with SO2, the rate acceleration [20,000 times for W(tj -CsH5)(Me)(CO)3] can be explained by an increase of the electrophilic character of sulfur in the presence of the Lewis acid. Insertion of the chalcogen dioxides EO2 has been reported with the tropylium derivative of molybdenum(O) Mo(>7 -C7H7)(R)(C0)2 ... 

B7.26 Chalcogen clusters of chromium, molybdenum, tungsten and rhenium... 

A few metal complexes of selenothioic and diselenoic acids have been reported. In a study on the reactivity of metal-carbon triple bond compounds toward chalcogens, it was found that molybdenum (52) and tungsten (53) carbyne complexes reacted with elemental selenium to yield the corresponding di-selenoate complexes 54 and 55, respectively (Eqs. 13 and 14) [18]. 

Chalcogen incorporation was monitored in the syntheses in Scheme 5.10 compound labels 40-44 in this scheme refer to general cluster core configurations without specific reference to terminal ligands. All reactions involved heterometallic clusters prepared from the facially chelated mononuclear molybdenum or tungsten trisulfide species 38 and 39, and from the previously described MoFe3S4 cubane 12-Mo site-specific... 

MOLYBDENUM AND TUNGSTEN CLUSTERS AS AQUA IONS [M3Q4(H20)9] + (M = Mo,W Q = S,Se) AND RELATED CHALCOGEN-RICH TRINUCLEAR CLUSTERS... 

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