Remote substituent effects on homolytic Fe‐N bond energies of p ‐G‐C 6 H 4 NHFe(CO) 2 (η 5 ‐C 5 H 5 ) and p ‐G‐C 6 H 4 (COMe)NFe(CO) 2 (η 5 ‐C 5 H 5 ) studied using Hartree–Fock and density functional theory methods

The nature and strength of metal–ligand bonds in organotransition–metal complexes is crucial to the understanding of organometallic reactions and catalysis . The Fe‐N homolytic bond dissociation energies [Δ H homo (Fe‐N)′s] of two series of para‐substituted Fp anilines p ‐G‐C 6 H 4 NHFp [1] and p ‐G‐C 6 H 4 N(COMe)Fp [2] were studied using the Hartree–Fock (HF) and the density functional theory methods with large basis sets. In this study, Fp is (η 5 ‐C 5 H 5 )Fe(CO) 2 and G are NO 2 , CN, COMe, CO 2 Me, CF 3 , Br, Cl, F, H, Me, MeO and NMe 2 . The results show that BP86 and TPSSTPSS can provide the best price/performance ratio and accurate predictions of Δ H homo (Fe‐N)′s. B3LYP can also satisfactorily predict the α and remote substituent effects on Δ H homo (Fe‐N)′s [ΔΔ H homo (Fe‐N)′s]. The good correlations [ r  = 0.96 (g, 1), 0.99(g, 2)] of ΔΔ H homo (Fe‐N)′s in series 1 and 2 with the substituent σ p + constants imply that the para‐substituent effects on Δ H homo (Fe‐N)′s originate mainly from polar effects, but those on radical stability originate from both spin delocalization and polar effects. ΔΔ H homo (Fe‐N)′s(1,2) conform to the captodative principle. Insight from this work may help the design of more effective catalytic processes. Copyright © 2012 John Wiley & Sons, Ltd.