A systematic study of the stabilities of cyclic boryl anions.

In this study, we perform several DFT functionals and post-SCF methods (MP2 and CCSD(T)) to investigate the stability of a series of virtual cyclic boryl anions. This investigation stems from two aspects: (1) the energetic difference between S(0) and T(1) states and (2) the electron affinity of the cyclic boryl anions. The results are systematically discussed in terms of substitution effect, influence of the steric effect, number of nitrogen atoms, the ring size and solvation inclusion. Moreover, the effect of the counter cation Li(+) on the singlet-triplet splitting is also investigated. Among various boryl anions studied, the results predict bulky-group substituted 5i and 8, shown in Schemes 3 and 4, respectively, to be stable anions in gas phase as well as in organic solvents. Since boryl anions may be exploited to synthesize new boron-containing compounds as well as to provide synthetic routes different from traditional protocols, the predicted thermodynamically stable 5i and 8 are then of both synthetic interest and challenging for future applications of cyclic boryl anions.