CO_4(CO)_8(μ_2-CO)_2(μ_4-E)_2(E:-PLi,-Pph,-POC_3H_7,-PF,-S,-Te)系列分子电子结构与催化性能的关系

Electronic Structure and Catalyzing of Clusters Co_4(CO)_8(μ_2—CO)_2(μ_4—E)_2(E:—PLi,—Pph,—POC_3H_7,—PF,—S,—Te)

本文用DV—X_a方法计算了系列簇合物分子Co_4(CO)_6(μ_2-CO)_2(μ_4-E)_2(E:-PLi、-PPh、-POC_3H_7、-PF、-S、-Te)的电子结构.簇合物的分子轨道能级分布大体可分为五个占据轨道能级区.计算结果表明:四桥合磷原子所带基团(R)对整体分子电子结构依电负性的大小为规律性的影响.从分子轨道的特征原子轨道可见Co—Co特征成键分子轨道能级较相应Co—P键的能级为高,并二者存在一较显著的能级间隔.两特征键与其醛化催化性能即活性及寿命相关联.对于不同四桥合原子的系列分子中,分子内P……P距离显著为短的事实可归因于桥合磷原子有效多的s,d原子轨道参与了分子轨道.

The electronic structures of the molecules Co_4(CO)_6(μ_2—CO)_2(μ_4—E)_2(E:—PLi,—PPh,—POC_3H_7, —PF,—S,—Te) have been calculated by using the SCC—Xa—DV method.The energy level diagrams of their molecular orbitals are similar to energy bands in solids and are roughly classed into five energy level groups.The calculated results show that R group in PR ligand on the molecular electronic structure is regular in the light of itself electronegativity.When we look for the atomic orbital characters,the molecular orbital energies belonged to Co—Co bonding are higher than those belonged to Co—P bonding.And furthermore, there is a gap between the two energy level groups which mainly determine the catalytic activity and the age of these clusters as catalysts in hydroformylation of olefins,respectively.Among the clusters,uncommonly short p……p distance in the molecule is attributed to more s,d atom orbitals taking part in the molecular orbital for P atom than for S atom and Te atom.