(1,3,5-C3P3H3)M与(1,3,5-C3P3H3)2M (M=Ti,V, Cr)配合物的结构与芳香性

运用密度泛函理论研究了(1,3,5-C3P3H3)M和(1,3,5-C3P3H3)2M (M=Ti,V,Cr)的结构、键合能以及芳香性.结果表明:低自旋的(1,3,5-C3P3H3)M和(1,3,5-C3P3H3)2M基态结构分别具有C3v和D3h对称性.金属与配体间为共价作用,二者之间存在σ、π和σ三种成键方式.V的三明治配合物的解离方式与Ti和Cr的三明治配合物不同,前者为分步解离,后两者则为一步解离.其中(1,3,5-C3P3H3)2Cr(D3h)的第一解离能最大,配合物最稳定.这些三明治和半三明治配合物都具有中心芳香性、内芳香性和外芳香性,且中心芳香性均大于自由配体(1,3,5-C3P3H3)的中心芳香性,芳香性主要贡献来源于π键和金属原子的孤对电子.内芳香性按照Ti、V、Cr的顺序依次增大,且内芳香性明显要大于外芳香性.高自旋的半三明治(1,3,5-C3P3H3)Ti(C3,5A1)与单重态(1,3,5-C3P3H3)Ti (C3v,1A1)相比,配体的变形性增大,稳定性增加,且C平面中心芳香性和内芳香性均增大,但P平面的中心芳香性却降低.

Structures and Aromaticities of Complexes (1,3,5-C3P3H3)M and (1,3,5-C3P3H3)2M (M=Ti, V, Cr)

The equilibrium geometries, binding energies and aromaticities of (1,3,5-C₃P₃H₃)M and (1,3, 5-C₃P₃H₃)₂M (M=Ti, V, Cr) were calculated by density function theory. The results indicate that the ground states of (1,3,5-C₃P₃H₃)M and (1,3,5-C₃P₃H₃)₂M have C_3v and D_3h symmetries, respectively. The main interactions between the ligands and metal are covalent interactions featuring three types of interactions represented as σ, π and δ between the ligands and the metal. The dissociation method of the ligands and the metal in sandwich V complexes is different from that of Ti and Cr complexes, i.e., the former consists of two steps and the latter consists of one step. The first dissociation energy of (1,3,5-C₃P₃H₃)₂Cr is the largest and so it is the most stable one. These complexes have central, inner and outer aromaticities and the central-aromaticities of the complexes are stronger than that of (1,3,5-C₃P₃H₃). The contributions of aromaticities is dominated by π bonds and the lone pair electronics of the metal atom. The inner-aromaticities of the complexes increase in the following order: Ti, V, Cr, and they are evidently stronger than the outer-aromaticities. Compared with (1,3,5-C₃P₃H₃)Ti (C_3v, ¹A₁) the distortion of the ligands for the high spin multiplicity of half-sandwich (1,3,5-C₃P₃H₃)Ti (C₃, ⁵A₁) is larger and more stable. The central and inner aromaticities in the C plane of the high spin multiplicity half-sandwich (1,3,5-C₃P₃H₃)Ti (C₃, ⁵A₁) are stronger than that of (1,3,5-C₃P₃H₃)Ti (C_3v, ¹A₁), but the central aromaticity in the P plane is weaker.