Bonding of Early-Metal Alkoxides

Several common synthetic strategies for the formation of transition metal-heteroatom bonds can be used for the preparation of early transition metal alkoxides, as shown in Equation 4.57. These methods include (1) metathesis between metal halides and alkali metal salts of the corresponding alcohols (2) direct reaction of the alcohols with metal halides in the presence of a base and (3) protonolysis of metal alkyls, amides, or alkoxides with more acidic alcohols. 

In addition, some less common reactions can be used to form early metal alkoxides. For example, the formation of metal alkoxides by insertions of a ketone into a metal-alkyl 

Various cyclopentadienyl-ligated early metal and actinide alkoxides were prepared by reactions of the alcohols with the metal hydride precursors to eliminate hydrogen gas,266,275,277,278 g j.jy metal alkoxides, as well as their high-valent late-metal analogs, can also be formed by attack of an alkyl group at an oxo ligand, where the alkyl could be added as a carbocation, a radical, or a carbanion (Equation 4.59).  

Early-transition-metal-alkoxo complexes are also stable toward other typical organome-tallic processes, such as reductive elimination. Hydridometal-alkoxo, alkylmetal-alkoxo, and arylmetal-alkoxo complexes of the early metals are known, but none of them undergoes reductive elimination to form a carbon-oxygen bond. Early-metal-alkoxo complexes also do not tend to undergo migratory insertion processes. In fact, this lack of insertion was exploited by Jordan to illustrate coordination of alkenes to d metal centers.  

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