金属硼烷arachmo—P4M2B8和closo—MB10X2分子结构的键合研究

利用ＤＶ－Ｘα法计算了ａｒａｃｈｎｏ－（ＰＨ３）４Ｍ２Ｂ８Ｈ８（ｕ－Ｈ）２（Ｍ：Ｎｉ，Ｐｄ，Ｐｔ）和ｃｌｏｓｏ－（ＰＨ３）２ＭＢ１０Ｈ８Ｘ２（Ｍ：Ｆｅ，Ｒｕ，Ｏｓ；Ｘ：Ｃｌ，Ｂｒ，Ｉ，ＯＨ，Ｌｉ）系列分子的电子结构。结果表明在２类ａｒａｃｈｎｏ－Ｐ４Ｍ２Ｂ８和ｃｌｏｓｏ－ＭＢ１０Ｘ２主干结构中均有类似的２种Ｍ－－Ｂ键合：一是金属原子ｄ轨道相对配体原子轨道形成了全对称匹配分子轨道（ＭＯｓ）；二是部分

Electronic structure calculations for metallaboraneswith C2v arachno - P4M2B8 and closo - MB10X2 skeletons

The electronic structures of the series arachno(PH3)4M2B8H8(μ- H)2(M: Ni,Pd, Pt) and closo- (PH3)2MB10H8(OH)2(M: Fe, Ru, Os) and closo-(PH3)2RuB10H8X2(X: Cl, Br, I, Li ) model molecules have been calculated by DV-Xα method. The resultsshow that there are two different bonding forms between M and B atoms for both arachno -P4M2B8 and closo - P2MB10 skeletons. One is the whole symmetry - matched MOs formedbetween metal and its ligands, the other is the partial symmetry - matched MOS formed between metal and its ligands. The former gives rise to effective orbital overlapping populationbetween M and B atoms, but the latter does not. In arachno - P4M2B8 skeleton, there is notsignificant orbital overlaping population between M and B (Ⅱ) although there is a littleshorter distance between the two atoms than that between M and B ( I ). Oppositely, incloso- P2MB10 skeleton, M－B(Ⅱ) covalence bonding strength is very high, compared toM－B(Ⅰ) covalence bonding order which is nearly zero. These bonding features, of whichadjacent orbitals of atoms does not overlap effectively although the distance between them appears in the reasonable scale of bonding length, may lead to the difficulty in synthesizingarachno - P4Ni2B8 and closo - (PH3)2MB10H10 compounds.