Boranes amine, hydrogenation with

Figure 8.12 Proton affinity of B-H hydrogens in borane amines and nitrogen atoms in amines versus number of CH3 groups. (Reproduced with permission from ref. 22.)...

Primary and secondary amines react with 1,2-alkyl or aryldiboranes to give amine-borane adducts which, with appropriate thermal encouragement, evolve hydrogen and yield the corresponding aminoboranes. Amino-boranes generally exhibit a tendency to disproportionate by reversibly exchanging R (or Ar) for H on boron,... 

A boron analog - sodium borohydride - was prepared by reaction of sodium hydride with trimethyl borate [84 or with sodium fluoroborate and hydrogen [55], and gives, on treatment with boron trifluoride or aluminum chloride, borane (diborane) [86. Borane is a strong Lewis acid and forms complexes with many Lewis bases. Some of them, such as complexes with dimethyl sulfide, trimethyl amine and others, are sufficiently stable to have been made commercially available. Some others should be handled with precautions. A spontaneous explosion of a molar solution of borane in tetrahydrofuran stored at less than 15° out of direct sunlight has been reported [87]. 

Octaborane(12) is a strong Lewis acid forming 1 1 adducts with ethyl ether, trimethyl amine and acetonitrile 223>. With sodium hydride in ether, approximately two thirds of a mole of hydrogen per mole of octaborane(12) is produced but the product is said to be apparently identical with the product of the reaction of sodium amalgam with octa-borane(12) which produces no hydrogen 223>. 

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