Remote substituent effects on homolytic Fe-N bond energies of p-G-C6H4NHFe(CO)2(η5-C5H5) and p-G-C6H4(COMe)NFe(CO)2(η5-C5H5) studied using Hartree-Fock and density functional theory methods

The nature and strength of metalligand bonds in organotransitionmetal complexes is crucial to the understanding of organometallic reactions and catalysis. The Fe-N homolytic bond dissociation energies [?Hhomo(Fe-N)'s] of two series of para-substituted Fp anilines p-G-C6H4NHFp [1] and p-G-C6H4N(COMe)Fp [2] were studied using the HartreeFock (HF) and the density functional theory methods with large basis sets. In this study, Fp is (?5-C5H5)Fe(CO)2 and G are NO2, CN, COMe, CO2Me, CF3, Br, Cl, F, H, Me, MeO and NMe2. The results show that BP86 and TPSSTPSS can provide the best price/performance ratio and accurate predictions of ?Hhomo(Fe-N)'s. B3LYP can also satisfactorily predict the a and remote substituent effects on ?Hhomo(Fe-N)'s [??Hhomo(Fe-N)'s]. The good correlations [r?=?0.96 (g, 1), 0.99(g, 2)] of ??Hhomo(Fe-N)'s in series 1 and 2 with the substituent sp+ constants imply that the para-substituent effects on ?Hhomo(Fe-N)'s originate mainly from polar effects, but those on radical stability originate from both spin delocalization and polar effects. ??Hhomo(Fe-N)'s(1,2) conform to the captodative principle. Insight from this work may help the design of more effective catalytic processes. Copyright (c) 2012 John Wiley & Sons, Ltd.