32015-64-8Relevant academic research and scientific papers
Dialkylaminohydridophenoxyboranes. Convenient preparation and studies of intramolecular boron-nitrogen π bonding
Kovar, Roger A.,Waldvogle, Gene G.
, p. 2239 - 2243 (2008/10/08)
A convenient preparation of dialkylaminohydridophenoxyborane compounds (HBOC6H5NR'2) has been developed according to the following three-step sequence: (1) 4BF3 (etherate) + 3NaBH4 = 3NaBF4 + 2B2H6(g); (2) 1/2B2H6(g) + HNR'2 = H3BNHR'2; (3) H3BHNR'2 + HOC6H5 + heat = 2H2 + HBOC6H5NR'2; HNR'2 = HN(CH3)2, HN(C2H5)2, HN(i-C3H7)2, HN(n-C4H9)2, HN(CH2C6H5)2, HNC4H8, and HNC5H10. The final products are isolated in yields ranging from 70 to 90% by vacuum distillation at moderate temperatures. Molecular association and variable-temperature proton magnetic resonance studies of these compounds in benzene solution are consistent with a planar, monomeric configuration with considerable π interaction between boron and nitrogen and hindered rotation about this bond. The Lewis acid behavior of diisopropylaminohydridophenoxyborane toward ammonia and trimethylamine was determined using a tensimetric titration procedure. No evidence of interaction was observed with trimethylamine while a stable 1:1 adduct was formed in the case of the reaction involving ammonia: HBOC6H5N(i-C3H7)2 + NH3 = HBOC6H5N(i-C3H7)2-NH 3. The room-temperature proton magnetic resonance spectrum of the ammonia adduct of diisopropylaminohydridophenoxyborane has demonstrated relatively unrestricted rotation about the secondary amino nitrogen-boron bond.
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.
