A Density Functional Theory Study of η2 Acyl Bonding in Fe and Mn Carbonyl Complexes

Abstract

The stability of the η 2 -acyl-Fe(CO) 3 X (acyl = CH 3 C(O), C 2 H 5 C(O), C(CH 3 ) 3 C(O); X = H, I, CH 3 ) complexes relative to the respective η 1 -acyl-Fe(CO) 3 X complex and their alkyl isomers has been studied using density functional theory (DFT). The effect of an acetyl versus a propionyl group, and the effect of the nature of the substituent, X, on the stability of various isomers is considered. For the CH 3 substituent the effect of a t-valeryl ((CH 3 ) 3 CC(O)) group was also probed. The η 2 -(CH 3 ) 3 CC(O)Fe(CO) 3 CH 3 complex is the most stable of the iron complexes studied. The effect of the substituents on the energies of the molecular orbitals of the complexes provides insight into the energy ordering of the various isomeric structures. DFT calculations were also performed on the η 2 -CH 3 C(O)Mn(CO) 4 complex and its isomers. Good agreement is achieved with regard to these calculations and available experimental and theoretical data. Predictions are presented for the stability of η 2 -acyl-Cr complexes.