化合物Mo(CO)_n^+(n=1～6)构型和键解离能的密度泛函研究

A Density Functional Study on the Geometries and Bond Dissociation Energies of Mo(CO)_n^+ (n = 1 ~ 6) Compounds

采用DFT/B_3LYP方法研究了化合物Mo(CO)_n^+(n=1～6)的基态可能构型,对于各n值,基态可能构型(电子态)依次为:直线型(~6∑^+),直线型(~6∑_g^+),C_(2v)(~2A_2)或D_(3h)(~6A_1),D_(4h)(~4A_(lg)),C_(2v)(~2B_2)或 C_(4v)＇(~2B_1),D_(3d)(~2A_(lg)).计算结果表明,对于n≥3时,碎片离子的构型与体系自旋多重度关系敏感.进一步计算了Mo-CO键的逐级解离能,计算值与实验结果能较好吻合,并从Mo原子4d和5s轨道杂化角度来解释该键解离能随n值的非单调变化.

The ground geometries of Mo (CO)n+ ( n = 1 ~ 6) compounds were studied by using DFT/B3LYP method. The structure and ground state of each fragment ion are orD3h(6A1), D4h(4A1g), C2v(2B2) or C4v'(2B1), and D3d(2A1g) for n = 6 sequentially. The results indicatethat the geometry of each species (n≥3) is sensitive to the spin state. The sequential bond dissociation energies( D0 ) for CO-Mo (CO) n-1+ are also calculated, and the results are in good agreement with the experiment, while the D0 for n= 3 is too small. The D0 values varied nonmonotonically with the number of ligands were discussed in term of 5s4d hybridization of Mo atom. In addition, the relations between the number of CO and the stability of fragment ions were discussed by analyzing the spin multiplicities of the system.