乙硼烷(B_2H_6)在醚溶液中分解的理论研究

A DFT Study of Dissociation of Diborane (B_2H_6) in THF

以二甲醚模拟四氢呋喃在乙硼烷分解过程中的作用.B3LYP/6-31G^(?)的计算结果发现,乙硼烷的分解是一个两步过程,每一步中均有一个醚分子与一个硼原子形成硼氧配位键,且只有一个氢桥键断裂.第一步反应的活化能为42.30kJ·mol^(-1),第二步的为4.33kJ·mol^(-1).当考虑溶剂效应时,第一步的活化能更降低为28.03kJ·mol(-1).

The detailed dissociation mechanism of diborane (B2H6) in vacuum or in tetrahydrofuran (THF) media has been studied at B3LYP/6 - 31G* level with dimethyl ether to simulate the involved THF. All the calculations indicate a two - step mechanism for the dissociation. Only one H - bridge bond is broken and one B-O bond is formed in the each SN2 - like step. Comparing with the dissociation of B2H6 in vacuum or in hydrocarbon media, participation of Me2O significantly lowers the activation barriers in the process. The barriers are further lowered when solvent effect is taken into account (28.03 kJ· mol-1 for the first step and 21.00kJ·mol-1 for the second one) .