Cluster complexes metal alkoxides

Efforts to prepare new alkoxides continue and many complex metal alkoxides have been prepared. For example, several metal oxoalkoxide clusters have been prepared by Bradley et al. [14]. Aluminium oxoalkoxides such as OBu)j(OBUgOH and Aljg(0Et)2j04 have been reported in the literature [15]. 

The hydrolysis of metal alkoxides gives reactive M-OH bonds. It is followed by condensation and leads to the formation of larger species. Complexation leads to non reactive M-OX bonds which prevent condensation and favor the formation of smaller species. A large variety of oligomeric species can then be obtained upon hydrolysis and condensation. Molecular clusters or colloidal particles can be synthesized depending on the relative amount of hydrolysis (h=H20AI) and complexation (x=X/M). More condensed species are obtained as x decreases and h increases as shown by the following examples. 

High-Valence Metal Clusters. Structural properties of selected hexanuclear high-valence cluster complexes are described in Table 2.5. A series of molybdenum and tantalum derivatives of type [(M6Y8)X6] and [(M6Ys)L8] (M = Mo or W X = halide or alkoxide Y = halide or other monovalent anion and L = neutral Lewis-base) are known. The structures of these species are like that of the anion [(Mo6Cl8)Cl6] illustrated in Fig. 2.19 in which the molybdenum atoms are in the vertex of an octahedron. Metal-metal distances of about... 

Treatment of 3 with NH4PF6 (3 equiv.) in methanol affords a trinuclear di(/t3-methoxo) complex 73 in high yield (Equation (25)). Analogous /r3-oxo-/t3-alkoxo clusters 75a and 75b are prepared by the reactions of (Cp Ru)2(/r-H)2(/tt-OCOCF3)2 74 with alkalis metal alkoxide MOR (R = Pr and Bu, M = Na and K) in the corresponding alcohol or THF (Equation (26)). Complexes 75a and 75b are also prepared by the treatment of 1 with NaO Pr and KO Bu, respectively. These complexes have been characterized by X-ray diffraction studies. 

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... 

---