32015-61-5Relevant academic research and scientific papers
A convenient synthesis of aminoboranes
Kovar, Roger A.,Culbertson,Ashby
, p. 900 - 905 (2008/10/08)
Detailed studies of the synthesis of aminoboranes by the reduction of phenyl borate with aluminum and hydrogen in the presence of secondary amines have been carried out. The amines used were diethylamine, diisopropylamine, and piperidine and the nature of the product formed was found to be a function of the phenyl borate : amine ratio. For example, tris(diethylamino)borane (81%) is prepared in admixture with bis(diethylamino)borane (5%) when diethylamine is used as the solvent whereas bis(diethylamino)borane is prepared exclusively and in high yield (80%) when phenyl borate and diethylamine are employed in a 1:2 molar ratio in benzene solvent. Aluminum-hydrogen reduction of equimolar quantities of phenyl borate and diethylamine in benzene solvent did not afford a high yield of the expected diethylaminoborane. Instead, nearly equimolar quantities of diethylaminohydridophenoxyborane [HB(OC6H5)N(C2H5)2] and diethylaminobis(phenoxy)borane [B(OC6H5)2N(C2H5) 2] were isolated. This reaction was found to be insensitive to changes in reaction time or temperature. The reaction sequence proposed to explain formation of the latter products involves (1) intermediate formation of AlH3 [Al + 3/2H2 → AlH3], (2) reaction between AlH3 and diethylamine forming the more thermodynamically stable bis(diethylamino)alane AlH3 + R2NH → AlH3NR2H → -H2 H2AlNR2 → -H2 R2NH HA1(NR2)2 and (3) reduction of phenyl borate by bis(diethylamino)alane [2B(OC6H5)3 + HAl(NR2)2 → HB(OC6H5)NR2 + B(OC6H5)2NR2 + Al(OC6H5)3]. Exchange studies between a number of aminoalanes and borate esters were also carried out.
