Cr(CO)_n(n=1-5)与C_6 H_6相互作用的密度泛函研究

用密度泛函理论在B3LYP/LANL2DZ基组水平上对(η~x-C_6H_6)Cr(CO)_n(x=1-6;n=1-5)复合物体系的可能构型进行了自由优化及相互作用能的计算,研究了不同羰基数对复合物稳定性、苯和羰基铬相互作用的影响,并对苯和羰基铬相互作用进行了NBO分析。得到以下结论:(1)当n≤3时,苯与Cr(CO)_n以η~6配位;当n≥4时,苯与Cr(CO)_n以η~2配位;(2)最稳定复合物中随羰基数的增加Cr-C_(benzene)平均键长增长,最大二面角H-C-C-H偏离碳环的角度随复合物对称性降低而逐渐增大;(3)当n为奇数时,复合物相互作用主要表现为苯C-C键的π轨道和Cr-CO键的σ反键轨道;当n为偶数时,复合物相互作用主要表现为苯C-C键的π轨道或π~*轨道与Cr的孤对电子轨道;(4)复合物羰基数越多,最稳定复合物的相互作用能数值越大,稳定性越小。

Density functional theory study of interactions between C_6 H_6 and Cr(CO)_n(n=1-5)complexes

In order to study the effects of a number of CO group on the Cr(CO)_n-C_6H_6 interactions,the structures of(η~x-C_6H_6)Cr (CO)_n(X=1-6;n=1-5)complexes were studied by using the density functional theory B3LYP method with LANL2DZ basis set.Natural bond orbital(NBO)analyses were also performed to explain the nature ofthe Cr(CO)_n-C_6H_6 interactions.The conclusions can be drawn as follows:(1)the most stable geometries of Cr(CO)_n-C_6 H_6 complexes are the configuration of(η_6-C_6H_6)Cr(CO)_n when n value is from 1 to 3 and(η~2-C_6H_6)Cr(CO)_n when n value is from 4 to 5.(2)With the carbonyl number increasing,Cr-C_benzene average bond length is lengther,the most dihedral angel is larger with the symmetry group reducing of complexes.(3)Through the Cr(CO)_n-C_6H_6 interactions,there is the great charge transfer from π bond of benzene towards σ_Cr-CO of Cr(CO)_n whe n os odd number,however there is interaction between π or π* bond of benzene and lone pair electron d orbital of Cr atom.(4)The more CO group there are,the lower is the stabilitity of the complex.