Amine borane, hydrogenation with

Boric acid may be similarly reduced to BjH under basic conditions on a large scale. Hydrogen in the presence of Al reduces borates to boranes quantitatively. These bo-ranes are trapped as the amine borane, e.g., phenylborate is dissolved in triethylamine and to the solution is added activated Al powder and small amounts of AICI3 catalyst. The mixture is agitated at 180°C for 1 h at 14.2 MPa of Hj. Quantitative yields of the (CH3)3NBH3 species are available from this process with a lower yield of C5N5N(CH3)2BH3 ... 

The B—C bond may be reduced in the presence of Hj at high P and T to afford boranes, e.g., alkylboranes and arylboranes are converted to organodiboranes and, in the presence of amines, to amine boranes , and also in processes in which solid borane polymer is formed from liquid organoboranes and Hj at 200°C. Partial hydrogenation of trialkylboranes to dialkylboranes is effected by treatment of the borane with Hj gas at 30.4 MPa and 120-200°C. Amine complexes of haloboranes are reduced by Hj gas to R3NBH3 species and ultimately to diborane . Amine complexes of triorganoboranes are aJso converted to amineborane by reaction with Hj gas. Finally, tetrahalodiboranes(4) are converted to the dihaloboranes by reaction with Hj below 0°C. The HjBX species disproportionate to yield ultimately BjH and BX3. 

The course of the reaction between halogenoboranes and the aminoben-zonitriles depends upon the position of the NH2 group.169 With the 3- and 4-amino-derivatives the products are the corresponding amine-boranes and compounds obtained by loss of hydrogen halide, (25) and (26). With the 2-amino-benzonitrile, however, the nitrile group is inserted into a B-halogen... 

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