配体稳定的二元过渡金属团簇[PdAu8(PR3)8]2+(R=Me,OMe,H,F,Cl,CN)的量子化学理论研究

采用从头计算MP2方法和密度泛函理论方法,对过渡金属团簇PdAu8(PR3)8]2+(R=Me,OMe,H,F,Cl,CN)的几何结构、电子结构以及团簇各组成部分之间的结合能进行了研究.MP2方法和SVWN局域泛函能够对团簇的结构给予准确的描述,而离域泛函BP86,PBE,BLYP和杂化泛函B3LYP则过高地估计了团簇的几何结构参数.电子结构研究表明Pd,Au原子通过d电子的成键作用构成团簇内核PdAu8]2+,PdAu8]2+与PR3配体则通过"σ给予/π反馈"模式成键.PR3配体与PdAu8]2+的结合能够加强Pd-Au之间的成键作用,增大前线轨道能级间隙,从而提高团簇的稳定性.PR3配体中 R 基团供、吸电能力的变化对PdAu8(PR3)8]2+结构的影响较小,但对PdAu8]2+ -pR3结合能的影响较大.能量分析显示不同PR3与PdAu8]2+之间具有相近的轨道作用能,与R基团供、吸电能力相关的非轨道作用能成为影响两者连接牢同程度的决定因素.

Theoretical Investigations on Ligand-stabilized Binary Transition-metal Cluster[PdAu8(PR3)8]2+ (R=Me,OMe,H,F,Cl,CN)

The molecular geometric and electronic structures of ligand-stabilized binary transition-metal cluster PdAu8(PR3)8]2+ (R=Me,OMe,H,F,Cl,CN) have been investigated by means of ab initio MP2 and density functional theory (DFT) methods.The bonding energies of Pd-Aus(PR3)82+ and PdAu8]2+ -PR3 have been also analyzed on the basis of calculations.The MP2 and local density functional SVWN methods have good performance in reproducing the experimental geometric features.The non-local exchangecorrelation functionals,such as BP86,PBE and BLYP,and hybrid functional B3LYP tend to overestimate the Pd-Au and Au-Au bond lengths.The studies of the electronic structures show that the metal cluster core PdAu8]2+ was formed by the d-d electron interaction of Pd and Au atoms.The bonding of PdAu8]2+ -PR3 complexes can be described as a synergistic combination of σ-donor and π-acceptor interactions between PdAu8]2+ and PR3 ligands.Adding the PR3 ligands led to the increases of the bonding interaction of Pd-Au and the HOMO-LUMO gap and,therefore,also the increase in the stability of the cluster.It was found that the effect of the electron donating or withdrawing ability of PR3 groups on the geometries of PdAu8(PR3)8]2+ was small,but that on the bonding energies of PdAu8]2+ -PR3 was large.The energy decomposition analysis results show that the orbital interaction energies of the PdAu8]2+ -PR3 bonding are very close to each other,so the magnitude of the non-orbital interaction energy plays a crucial role in the stabilization of PdAu8(PR3)8]2+ complexes.