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Metal oxo-alkoxides

The last decade has witnessed mushrooming growth (4, 23, 42, 504) in X-ray structural determinations (Table VI) of metal oxo-alkoxide complexes. [Pg.405]

Figure 72. The common X-ray established structural types of oxo ligands identified in metal oxo-alkoxides. Figure 72. The common X-ray established structural types of oxo ligands identified in metal oxo-alkoxides.
Single metal and mixed metal oxo alkoxides can also be prepared by reaction between metal halides, oxy halides, and alkali metal alkoxides.47,48 One of the first to be structurally characterized was a series of mixed Cd or Sn containing zirconium, tin, and titanium alkoxides.84,85 These and other examples are shown in skeletal form in Figure 3. [Pg.717]

Metal oxo-alkoxides, MO (OR)x 2 > , may be considered intermediates between metal alkoxides M(OR)x and the corresponding metal oxide, and are the counterparts of the polyanions and polycations in aqueous systems. Controlled partial hydrolysis of M(OR)x (Equation (20)) does indeed sometimes result in structurally well-defined metal oxo-alkoxo oligomers (clusters) where //2—0x0 ligands connect the metal polyhedrons from which the clusters are constructed. [Pg.643]

Although hydrolysis/condensation is the normal route leading to metal oxo-alkoxides, ether cleavage (Equation (21)) is another possibility for the formation of such species. [Pg.643]

Metal Oxo Alkoxides are implicated as intermediates in the hydrolysis of metal alkoxides to metal oxides and their importance in the sol-gel process has led to much research activity in this area. Accordingly we have allocated a whole chapter to the Metal Oxo Alkoxides. [Pg.1]

In restrospect, the isolation of oxo-aUcoxide products, in the straightforward reactions of metals with alcohols has generated a new interest in metal oxo-alkoxide products (Chapter 5), a large number of which have been reported in the extensive investigations of Turova et employing the solubility and vapour pressure studies of... [Pg.17]

The hydroxo-metal alkoxides (A) tend to react further in two ways (Eqs 2.191 and 2.192) to form the metal oxo-alkoxide derivatives. [Pg.108]

Under carefully controlled conditions, however, intermediate metal oxo-alkoxides, MOj,(OR)j-2y may be isolated. (See also Chapter 5.)... [Pg.109]

A detailed mechanistic study of hydrolysis reactions was made by Bradley who had isolated a number of metal oxo-alkoxides and assigned plausible strucmres for such products. There has been a renewal of interest in the chemistry of metal oxo-alkoxides (Chapter 5), some of which have been isolated under anhydrous conditions also. Further, these hydrolysis reactions have assumed unprecedented technological significance in view of their importance in the preparation of ceramic materials by the sol-gel process (Chapter 7) which involves controlled hydrolysis of metal alkoxides (or some other precursors). [Pg.109]

Metal oxo-alkoxides [MOj(OR)(j, 2 c)]j may be regarded as intermediates between the oligomeric metal alkoxides [M(OR)j,]n(JC = 0) and the three-dimensional macromolec-ular metal oxides [MOy/2] x =y /2 y = oxidation state of M). Indeed most metal alkoxides are readily converted by hydrolysis to the corresponding metal oxide (Eq. 5.1). [Pg.383]

Apart from the pioneering researches of Bradley and co-workers, who studied the controlled hydrolysis of the alkoxides of some early transition metals, there was little interest in the metal oxo-alkoxides until the sol-gel technique was developed for the conversion of metal alkoxide precursors into metal oxides and heterometal oxides (Chapter 7) A concise review of the chemistry of metal oxo-alkoxides published by Mehrotra and Singh" reveals the rapid growth of interest in this field. The most notable feature has been the dramatic increase in the number of crystal structure determinations in recent years. However, our knowledge of the mechanism of formation of metal oxo-alkoxides leaves much to be desired. [Pg.383]

Although the hydrolysis of a metal alkoxide is the obvious route to the formation of a metal oxo-alkoxide other methods have been identified and these will also be mentioned. [Pg.383]

Metal oxo-alkoxides unintentionally obtained during attempts to prepare metal alkoxides have generally resulted from the presence of adventitious water leading to hydrolysis, but it appears that the formation of some oxo-alkoxides is due to the instability of the sought after alkoxide. [Pg.385]

An alternative approach to the synthesis of metal oxo-alkoxides involves the reaction of the metal oxo-chloride with the requisite amount of sodium alkoxide (Eq. 5.25) ... [Pg.388]

Preparation of Metal Oxo-alkoxides from Metal Oxides... [Pg.389]

The further hydrolysis of metal oxo-alkoxides to produce metal oxides is of considerable importance in the sol-gel process. [Pg.390]

Alcohol exchange of metal oxo-alkoxides has also been studied. Thus the molybdenum oxo-alkoxides [Mo02(OR>2] (R = Pr, CH2Bu ) were obtained from the tertiary butoxo compound (Eq. 5.30). " ... [Pg.390]

NMR spectroscopy has played an increasingly important role in characterizing metal oxo-alkoxides since the 1970s. In principle the environments of the alkyl groups may... [Pg.391]

Mass spectral studies on metal oxo-alkoxides have sometimes given valuable analytical data. As with metal alkoxides the parent molecular ion P = [M OyCOR) ] is usually of very low intensity and the strongest high mass fragment ion is often P — Me, P — R, or P - OR. [Pg.393]

In the 1978 book Metal Alkoxides only three authentic X-ray crystal structures of metal oxo-alkoxides were described, namely [V2(0)2(0Me>6], [Ti704(OEt)2o], and [Nb80io(OEt)2o]. Since then there has been an explosive growth in the nnmber of structure determinations with examples of Hs-O, H4-O, fi-O, and Ot... [Pg.396]

In the metal (and heterometal) oxo-alkoxides the metals adopt coordination numbers that are common in the parent metal alkoxides, but the presence of the 0x0 ligand, with its ability to bond to six metals (/xe) in the centre of a molecnle, is often structure determining. Since the emphasis in this section is on the behavionr of the 0x0 ligand rather than the metal the stmctures of heterometal oxo-alkoxides will be considered together with those of the metal oxo-alkoxides. Owing to the very large number of structures known, only a few will be considered in detail and the data on the majority will be tabulated. [Pg.396]

Although no alkali metal oxo-alkoxide has yet been structurally characterized the structure of the remarkable heteroalkali metal complex [Li8K2(0)(0Bu )8(Me2NC2H4NMe2)2]... [Pg.396]


See other pages where Metal oxo-alkoxides is mentioned: [Pg.60]    [Pg.409]    [Pg.629]    [Pg.643]    [Pg.646]    [Pg.4]    [Pg.383]    [Pg.384]    [Pg.385]    [Pg.387]    [Pg.389]    [Pg.391]    [Pg.391]    [Pg.391]    [Pg.393]    [Pg.393]    [Pg.396]    [Pg.397]    [Pg.399]    [Pg.403]    [Pg.405]    [Pg.409]    [Pg.411]    [Pg.417]    [Pg.419]    [Pg.425]   
See also in sourсe #XX -- [ Pg.4 , Pg.102 ]




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