Chemistry Department, University of Alabama, Shelby Hall, Box 870336, Tuscaloosa, Alabama 35487-0336, USA.
J Phys Chem A. 2010 Feb 25;114(7):2644-54. doi: 10.1021/jp9102838.
The energetics for different dehydrogenation pathways of C(2)B(2)N(2)H(12) and C(4)BNH(12) cycles were calculated at the B3LYP/DGDZVP2 and G3(MP2) levels with additional calculations at the CCSD(T)/complete basis set level. The heats of formation of the different isomers were calculated from the G3(MP2) relative energies and the heats of formation of the most stable isomers of c-C(2)B(2)N(2)H(6), c-C(2)B(2)N(2)H(12), and c-C(4)BNH(12) at the CCSD(T)/CBS including additional corrections together with the previously reported value for c-C(4)BNH(6). Different isomers were analyzed for c-C(2)B(2)N(2)H(x) and c-C(4)BNH(x) (x = 6 and 12), and the most stable cyclic structures were those with C-C-B-N-B-N and C-C-C-C-B-N sequences, respectively. The energetics for the stepwise loss of three H(2) were predicted, and the most feasible thermodynamic pathways were found. Dehydrogenation of the lowest energy c-C(2)B(2)N(2)H(12) isomer (6-H(12)) is almost thermoneutral with DeltaH(3dehydro) = 3.4 kcal/mol at the CCSD(T)/CBS level and -0.6 kcal/mol at the G3(MP2) level at 298 K. Dehydrogenation of the lowest energy c-C(4)BNH(12) isomer (7-H(12)) is endothermic with DeltaH(3dehydro) = 27.9 kcal/mol at the CCSD(T)/CBS level and 23.5 kcal/mol at the G3(MP2) level at 298 K. Dehydrogenation across the B-N bond is more favorable as opposed to dehydrogenation across the B-C, N-C, and C-C bonds. Resonance stabilization energies in relation to that of benzene are reported as are NICS NMR chemical shifts for correlating with the potential aromatic character of the rings.
采用 B3LYP/DGDZVP2 和 G3(MP2) 水平计算了 C(2)B(2)N(2)H(12) 和 C(4)BNH(12) 循环的不同脱氢途径的能量，并用 CCSD(T)/完全基组水平进行了额外计算。不同异构体的生成热是根据 G3(MP2) 相对能和最稳定的 c-C(2)B(2)N(2)H(6)、c-C(2)B(2)N(2)H(12)和 c-C(4)BNH(12)异构体的生成热计算的，这些异构体的生成热是在 CCSD(T)/CBS 水平上包括与之前报道的 c-C(4)BNH(6)值一起进行的附加修正计算的。对 c-C(2)B(2)N(2)H(x)和 c-C(4)BNH(x) (x = 6 和 12)的不同异构体进行了分析，最稳定的环状结构分别是具有 C-C-B-N-B-N 和 C-C-C-C-B-N 序列的结构。预测了逐步失去三个 H(2)的能量，找到了最可行的热力学途径。最低能量 c-C(2)B(2)N(2)H(12)异构体(6-H(12))的脱氢几乎是热中性的，在 CCSD(T)/CBS 水平下的 DeltaH(3dehydro)为 3.4 kcal/mol，在 G3(MP2)水平下为-0.6 kcal/mol，在 298 K 下。最低能量 c-C(4)BNH(12)异构体(7-H(12))的脱氢是吸热的，在 CCSD(T)/CBS 水平下的 DeltaH(3dehydro)为 27.9 kcal/mol，在 G3(MP2)水平下为 23.5 kcal/mol，在 298 K 下。与 B-C、N-C 和 C-C 键相比，B-N 键的脱氢更有利。报道了与苯的共振稳定能的关系，以及与环的潜在芳香特征相关的 NICS NMR 化学位移。
