Some Recent Developments in Hydrogenation Activation of Hydrides by Transition Metal Derivatives

Some Recent Developments in Hydrogenation Activation of Hydrides by Transition Metal Derivatives 

Activation of hydride reagents such as NaH, LiAlH4, NaBH4, etc. by TM complexes has attracted much attention in recent years and considerably extended the scope of their use. Not only are such reagents attractive because of their ease of handling and low costs, but also because of their versatility and the many variations possible. By careful choice of catalyst system, a remarkable degree of selectivity can be attained, often under mild conditions. 

Systems are known which will reduce most of the organic functions (amides, carboxylic acids, nitriles, nitro, halides, double and triple bonds, aromatic rings, for instance). In most cases, the true catalyst is formed in situ by reduction of the metal with the hydride. Actually, very little is known of the mechanisms of those transition metal-assisted hydride reductions. Catalyzed reductions with NaBH4 have been reviewed [7]. 

The following examples illustrate the versatility and potentialities of such processes. 

LiAlH with First Row Transition Metal Halides 

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