METAL-PHOSPHORUS BONDING IN FE(CO)(4)PR3 COMPLEXES - A DENSITY-FUNCTIONAL STUDY

Fe(CO)(4)PR3 complexes have been studied for R = H, Me, Ph, OMe, F, i- Pr, and NC4H4 using density functional methods. The Fe-PR3 bond has be en analyzed in terms of steric and electronic effects. The results obt ained show that the main contribution to the bond stems always from th e sigma donation, but phosphines can be classified into three groups d epending on the relative magnitude of the pi-back-donation contributio n. Thus, PMe3, PPh3, and P(i-Pr)(3) can be considered as sigma-donor l igands, PF3 and P(NC4H4)(3) would be sigma-donor/pi-acceptor ligands, and PH3 and P(OMe)(3) would correspond to intermediate cases.