第一过渡系金属硅烯配合物的理论研究

以HF/6-311 G^*基组研究了硅烯SiH2同第一过渡系金属的配合物MSiH2的分子轨道特征及键解离能,MSiH2为共平面构型,基保基态的^3TiSiH2 和^4CoSiH2带有明显的双键特征,M-Si键具有共价性质,M-Si的键解离能,从Sc到Cu呈现周期性变化,这种变化趋势同M的金属离子激发能之是存在近似的线性关系.

Theoretical Study of the Complexes of First-row Transition Metals with SiH2

The HF/6-311+G* basis set was used to study the characteristics of molecular orbitals and bond dissociation energies of the complexes, MSiH2, of the first-row transition metals with SiH2. The atoms in MSiH2 are all coplanar, and M—Si bonds of ground state 3TiSiH2 and 4CoSiH2 show obviously the double bond characteristic. In 4VSiH2 and 5CrSiH2 there is the week single occupied π bond. The 8MnSiH2 with a high-spin eightet ground state has both of single occupied σ and π bonds, and chief component of its σ and π orbital are the Mn 4s and the Si 3px orbitals, respectively. Other ground state MSiH2 have only a double occupied σ single bond. The most of M—Si bonds are quite covalent. The formation of M—Si σ bonds can be considered as the interaction between one electron in 4s or 4pz, or 3d orbital of M and other electron in Si sp hybrid orbital. The double occupied π bonds are also considered as the pairing of one π electron of SiH2(3B1) with one 3d electron of M. All of the HSiH bond angles in MSiH2 are closed to that in SiH2(3B1). It means that the Si in MSiH2 still keeps a sp hybrid orbital similar to Si in SiH2(3B1 states). The Sc—Si, V—Si and Ni—Si bonds are longer because their formation involves mainly the 4s orbitals of M. On the contrary, the Cu—Si bond is shorter since its σ bond would involve primarily the M 3dZ2 \{obitals\}. The 3TiSiH2 and 4CoSiH2 have much shorter bond lengths and larger bond dissociation energies because of their double bond character. From Sc to Cu, the bond dissociation energies of M—Si change in periodic trend. There is an approximate linear relationship between the bond dissociation energies and the metal ion promotion energy.