Molybdenum clusters trinuclear

Trinuclear Molybdenum and Tungsten Cluster Chalcogenides From Solid State to Molecular Materials... 

During the past several years it has been shown that both molybdenum and tungsten in oxidation states of +4 or thereabouts, have marked predilection to form trinuclear duster species. For the tungsten cluster spedes, there are three different structural types with respect to the ligand arrangements (Figure 24 a, b, c) which are based on an equilateral triangle of M—M bonded atoms. Structure (a) contains th [W3(j 3-X)(ju-Y)3] nucleus, where X = 0, Cl,... 

Phthalic acid, with trinuclear Os clusters, 6, 743 n-acceptor carbon ligands, in molybdenum carbonyls, 5, 455 Ti-allyl complexes, with molybdenum with cyclopentadienyl-supporting ligands, 5, 544 monomeric complexes, 5, 546 oxide surface binding, 5, 546... 

Trinuclear clusters play an important role in the chemistry of molybdenum and tungsten. Deep red, isostructural clusters containing both [M03O4F9]3- (148, 149) and [W304F9]5 (149-151) are later additions to this family of simplest types of cluster species. Their basic structures conform to the fii-type of trinuclear electron-poor transition-metal clusters where the metals are in a distorted octahedral environment. 

It is also noteworthy that both molybdenum and tungsten carbonyls react with carboxylic acids to give excellent yields of another type of trinuclear cluster with equilateral triangles of metal atoms, in which the triangles are capped above and below by single oxygen atoms (52). 

Our relatively innocent venture into the chemistry of molybdenum oxide systems has led to the discovery of a whole new class of ternary oxide compounds dominated in their structural features by strong metal-metal interactions. Interest in the question of whether the trinuclear clusters in the well known compound Zn.Mo 0 (10, 11) could accept more than 6 electrons in the metal-... 

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. 

A second major type of oxo trinuclear cluster is the type with two ju.3-0 caps, formed equally by molybdenum and tungsten. They are usually obtained by treating M(CO)6 with a mixture of a carboxylic acid and its anhydride, RC02H/(RC0)20, pouring the reaction mixture, after dilution with water, on a cation exchange column... 

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. 

MOLYBDENUM AND TUNGSTEN 4.12.6.1 Trinuclear Clusters with M3Q44+ Core... 

Nitrogenase is another big target of cluster synthesis. The X-ray elucidation of the active center of the Fe-Mo cofactor and P-cluster (5) has accelerated the efforts to find rational preparative methods of trinuclear or cubane-type clusters containing molybdenum (6-9). The raft cores in these cluster complexes are one of the general structural units also in solid-state compounds, and the mutual relationships are very important. A number of review articles are now available on the syntheses, structures, and other properties of metal chalcogenide cluster compounds (6, 7,10-24). 

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