Substituent effects on gas‐phase homolytic Fe–N bond energies of m‐G‐C₆H₄NHFe(CO)₂(η⁵‐C₅H₅) and m‐G‐C₆H₄N(COMe)Fe(CO)₂(η⁵‐C₅H₅) studied using density functional theory methods

Abstract

One of the most fundamental properties in chemistry is the bond dissociation energy, the energy required to break a specific bond of a molecule. In this paper, the Fe–N homolytic bond dissociation energies [ΔHhomo(Fe–N)'s] of 2 series of (meta‐substituted anilinyl)dicarbonyl(η5‐cyclopentadienyl) iron [m‐G‐C6H4NHFp (1)] and (meta‐substituted α‐acetylanilinyl)dicarbonyl(η5‐cyclopentadienyl) iron [m‐G‐C6H4N(COMe)Fp (2)] were studied using density functional theory methods with large basis sets. In this study, Fp is (η5‐C5H5)Fe(CO)2, and G is NO2, CN, COMe, CO2Me, CF3, Br, Cl, F, H, Me, MeO, and NMe2. The results show that Tao‐Perdew‐Staroverov‐Scuseria, Minnesota 2006, and Becke's power‐series ansatz from 1997 with dispersion corrections functionals can provide the best price/performance ratio and accurate predictions of ΔHhomo(Fe–N)'s. The ΔΔHhomo(Fe–N)'s (1 and 2) conform to the captodative principle. The polar effects of the meta‐substituents show the dominant role to the magnitudes of ΔΔHhomo(Fe–N)'s. σα· and σc· values for meta‐substituents are all related to polar effects. Spin‐delocalization effects of the meta‐substituents in ΔΔHhomo(Fe–N)'s are small but not necessarily zero. RE plays an important role in determining the net substituent effects on ΔHhomo(Fe–N)'s. Insight from this work may help the design of more effective catalytic processes.