【摘要】 采用从头算Hartree-Fock(HF),M??ller-Plesset微扰(MP2),二级近似耦合簇(CC2)和密度泛函理论(DFT)方法,对IB族金属-乙烯配合物LM-C2H4(L=[N{(Me)C(Ph)N}2];M=Cu,Ag,Au)的几何结构、电子结构以及LM与C2H4之间的结合能进行了理论研究.MP2、CC2和密度泛函方法对C2H4配位前后C=C键长的变化情况都给出了正确的描述.电子结构分析显示LM与C2H4之间主要以C2H4→LM"σ-给予"和LM→C2H4"π-反馈"方式协同成键,这种成键方式使C2H4配体π轨道上的电子密度下降,π*轨道上的电子密度增加,并使得C=C键长增加、键能下降,从而达到活化C=C键的目的.自然电荷布居和能量分解分析显示LM-C2H4中的"σ-给予"作用弱于"π-反馈"作用,若使用"σ-给予"作用强于"π-反馈"作用的M+-C2H4体系作为LM-C2H4的简化模型进行理论研究是不合适的.LM-C2H4中金属原子M的改变对C=C键长、C2H4电荷布居以及LM与C2H4之间的结合能等性质影响显著.LAu与LCu、LAg相比其接受和反馈电子的能力最强,使C2H4配体π轨道电子密度减少的程度和π*轨道电子密度增加的程度也最大,因此LAu对C2H4中C=C键的活化效果最好.螯合配体取代基供、吸电能力的改变对上述性质的影响则非常有限.更多还原

【Abstract】 The geometries,electronic structures,and bonding energies of coinage metal-ethylene complexes LM-C2H4 (L=[N{(Me)C(Ph)N}2];M=Cu,Ag,Au)were investigated by Hartree-Fock,Mφller-Plesset perturbation(MP2),second-order approximate coupled-cluster(CC2),and density functional theory(DFT)methods.The MP2,CC2,and DFT methods performed well in reproducing the experimental geometric features of LM-C 2 H 4 .The bonding in LM-C2H4 can be described as a synergistic combination of σ-donor andπ-acceptor interactions between the LM and C2H4 π-system.Bothσ-donor andπ-acceptor contributions increased the C=C bond length and decreased the C=C bond strength by removing electron density from the bondingπorbital and increasing electron density in the anti-bondingπ*orbital, respectively.The results of natural population analysis and energy decomposition analysis show that the LM→C2H4 back-donation contribution to the LM-C2H4 bonding is higher than that of the C2H4→LM donation, but this order is reversed in the M + -C2H4 systems.Therefore,it is not appropriate to use M+ -C2H4 as a computational model for electronic structures studies of LM-C2H4 .The effects of changing the metal on the structural and electronic properties,such as C=C bond length,charge populations of C2H4 ,and LM-C2H4 interactions,were large.Compared with LCu and LAg,LAu had the strongest ability to accept and donate electrons.Consequently,it showed the maximum reduction in theπorbital electron density and increase in theπ*orbital density.Therefore,activation of the C=C bond by LAu was more effective than by LCu and LAg.However,the effects of electron donating or withdrawing ability of the auxiliary ligands on the above properties were small.更多还原