Metal−Phosphorus Bonding in Fe(CO)₄PR₃ Complexes. A Density Functional Study

Fe(CO) 4 PR 3 complexes have been studied for R = H, Me, Ph, OMe, F, i -Pr, and NC 4 H 4 using density functional methods. The Fe−PR 3 bond has been analyzed in terms of steric and electronic effects. The results obtained show that the main contribution to the bond stems always from the σ donation, but phosphines can be classified into three groups depending on the relative magnitude of the π-back-donation contribution. Thus, PMe 3, PPh 3, and P( i -Pr) 3 can be considered as σ-donor ligands, PF 3 and P(NC 4 H 4 ) 3 would be σ-donor/π-acceptor ligands, and PH 3 and P(OMe) 3 would correspond to intermediate cases.