Polarized multiple bonds metal hydrides

Hydride is added to the multiple bond (path AdN) as expected. Usually the metal cation complexes with the Y heteroatom nucleophilic attack on the polarized multiple bond will then yield a product that is stabilized by ion pairing. 

A number of metal hydrides have been employed as reducing agents in organic chemistry, but the most commonly used are lithium aluminium hydride and sodium borohydride, both of which are commercially available. These reagents are nucleophilic and as such they normally attack polarized multiple bonds such as C=0 or C=N by transfer of hydride ion to the more-positive atom. They do not usually reduce isolated carbon-carbon double or triple bonds. 

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