Fe(CO)3(PR3)2和Fe(CO)2(PR3)3的结构与性质的理论研究

采用B3LYP和BP86方法,对铁羰基衍生物Fe(CO)3(PR3)2和Fe(CO)2(PR3)3(R=Cy,OPh和Ph)的几何和电子结构、成键特点以及热力学稳定性等进行了理论研究.计算结果表明,Fe(CO)3(PR3)2的基态结构都为三角双锥的轴向双取代;对于Fe(CO)2(PR3)3来说,三角双锥的腰部三取代(D3h)和腰部+轴向双取代(C2v)结构能量差别非常小.自然键轨道(NBO)分析显示,膦配体向羰基铁基团存在电荷转移,使得Fe—CO之间的共价作用有效增强.含膦配体铁羰基化合物Fe(CO)3(PR3)2的第一膦配体解离能比第一羰基解离能低,预示Fe(CO)3(PR3)2的反应活性比Fe(CO)5有明显提高.

Theoretical study on the structures and properties of Fe(CO)3(PR3)2 and Fe(CO)2(PR3)3

The geometric structures, electronic configurations, bonding characteristic, and thermodynamic properties of iron carbonyl derivative complexes Fe(CO)3(PR3)2 and Fe(CO)2(PR3)3(R=Cy, OPh, Ph) were studied by using the B3 LYP and BP86 functional of density functional theory(DFT). The results show that the ground state for Fe(CO)3(PR3)2 are all axially double substitution of trigonal bipyramid structure. For complexes Fe(CO)2(PR3)3, the energy difference between the equatorial triple substitution and equatorial plus doubly axial substitution structures is very small. Natural bond orbital(NBO) analysis show that there is charge transfer from the phosphorus ligand(s) to the carbonyl iron fragment, which making the covalent interaction between Fe and CO be enhanced. The phosphorus ligand dissociation energy is lower than the first carbonyl dissociation energy from the most stable structure Fe(CO)3(PR3)2. This indicates that the reactivity of Fe(CO)3(PR3)2 is largely greater than Fe(CO)5. The purpose of this study is to understand the relationship between the molecular structure and property of Fe(CO)3(PR3)2 and Fe(CO)2(PR3)3, and provide some useful information for the design and synthesis of iron carbonyl derivatives.