硼烷分子中化学键性质的研究 Ⅲ.锥型分子B_3H_6X的结构与成键特征

Studies on the Nature of Chemical Bonding in Boranes III.The Structure and Bonding Behavior of Pyramidal B_3H_6X

用MP2/6-31G方法,对三角锥型分子B_3H_6X(X=B^(2-),C^-,N,O^+,BH^-,CH和NH^+)及其碎片B_3H_6和X的结构进行了ab initio研究.结果表明,当X=NH~_+,O^+和N时,B_3H_6基环上的端氢(H_t)朝着帽基X方向,而当X=CH,BH^-,B^(2-)和C^-时,H_t却转向帽基X的反向.这种特征可用配位原子的电负性和配位原子轨道的弥散性给以说明.我们还进一步研究了B_3H_6X系列化合物的结合能和稳定性.

Ab initio molecular orbital studies of pyramidal B3H6X structures (X = B2- ,C-, N, H+ ,BH- ,CH and NH+ ) indicate that,for structures where X= N,O+ and NH+ ,the terminal hydrogens (Ht) of the B3H6 ring are toward the direction of the apical X. In contrast,the H, are found to be away from the caping group for X = B2- , C- , BH- and CH. The binding energy of B3H6 ring with apical fragmentation X was calculated.