Theoretical Study on Structure and Property of Iron Carbonyl Derivatives Fe(CO)5-x(PR3)x

The geometric structures, electronic configurations, bonding characteristic, and thermodynamic properties of low valence iron complexes Fe(CO)(5-x)(PR3)(x) (x=1 similar to 3, R=H, F, Me) were studied using the density functional theory (DFT) method. The results show that the geometric framework of Fe(CO)(5-x)(PR3)(x) is not aberrant but maintain the distorted trigonal bipyramidal structure after the introduction of phosphorus ligand. Natural bond orbital (NBO) analysis show that there is charge transfer between the phosphorus ligand to the carbonyl iron fragment. Moreover, the covalent interaction between Fe and CO is enhanced. The phosphorus ligand dissociation energy is lower than the first carbonyl dissociation energy from the most stable structure Fe(CO)(5-x)(PR3)(x) This indicates that the reactivity of Fe(CO)(5-x)(PR3)(x) is largely greater than Fe(CO)(5).