Tungsten molecular structure

Figure If shows the molecular structure of the [Tc6Br6(/t3-Br)5]2- anion. In general, the structure of this anion is similar to the structure of the well-known octahedral halogenide clusters of molybdenum and tungsten [M6X8]4 + (X = Cl,Br, I) [5,8]. The principal difference is that the eight equivalent positions of bridging bromine atoms in the technetium clusters are not fully occupied.

In addition to the bimetallic complexes of rhenium and alkaline metals formed as byproducts in the exchange reactions of rhenium halids with alkali alkoxides (such as, for example, LiReO(OPr )5 xLiCl(THF)2 [519]) there has been recently prepared a number ofbimetallic complexes ofrhenium and molybdenum, rhenium and tungsten, and rhenium and niobium [904, 1451]. The latter are formed either due to the formation of a metal-metal bond, arising due to combination of a free electron pair on rhenium (V) and a vacant orbital of molybdenum (VI) atom or via insertion of molybdenum or tungsten atoms into the molecular structure characteristic of rhenium (V and VI) oxoalkox-ides. The formation of the compounds with variable composition becomes possible in the latter case. 

This section describes the structural chemistry of 14 molecular structures, 3 of chromium, 8 of molybdenum, and 3 of tungsten. The only binary xanthate structures are those of chromium, all other structures are at least ternary in nature. For the chromium and tungsten structures, conventional monodent-ate and bidentate coordination modes of the xanthate ligand are found. By contrast, a rich, diverse, and fascinating coordination range is observed for the... 

Fig. 0. Molecular structure of traws-(iodo)tetracarbonyl(phenylcarbyne)tungsten(0).

Fig. 10. Molecular structure of the zirconoxycarbene tungsten complex 104 obtained by diastereoselective alkylation of 103.

The Raman investigation of niobium species in aqueous solutions of niobium oxalate (Jehng and Wachs, 1991) nicely showed the dependence of their constitution on pH and concentration. The PZC theory was successfully applied to predict the hydrated, molecular structures of multicomponent supported metal oxide species, such as iron-molybdenum, iron-vanadium, molybdenum-vanadium, tungsten-vanadium, and sodium-vanadium oxide species (Vuurman et al., 1991 Wachs et al., 1993). 

The molecular structure of 9d (Fig. 3) reveals a pseudo-tetragonal pyramidal piano stool arrangement of the ligands at the central tungsten atom with the cyclopentadienyl ligand in the... 

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