Remote substituent effects on gas-phase homolytic Fe-O and Fe-S bond energies of p-G-C6H4OFe(CO)2(η5- C5H5) and p-G-C6H4SFe(CO) 2(η5-C5H5) studied using Hartree-Fock and density functional theory methods
- 医学院－已发表论文 
Metal-ligand bond enthalpy data can afford invaluable insights into important reaction patterns in organometallic chemistry and catalysis. In this paper, the Fe-O and Fe-S homolytic bond dissociation energies [ΔH homo(Fe-O)'s and ΔHhomo(Fe-S)'s] of two series of para-substituted phenoxydicarbonyl(η5-cyclopentadienyl) iron [p-G-C6H4OFp (1)] and (para-substituted benzenethiolato)dicarbonyl(η5-cyclopentadienyl) iron [p-G-C 6H4SFp (2)] were studied using Hartree-Fock and density functional theory (DFT) methods with large basis sets. In this study, Fp is (η5-C5H5)Fe(CO)2, and G are NO2, CN, COMe, CO2Me, CF3, Br, Cl, F, H, Me, MeO, and NMe2. The results show that DFT methods can provide the best price/performance ratio and accurate predictions of ΔH homo(Fe-O)'s and ΔHhomo(Fe-S)'s. The remote substituent effects on ΔHhomo(Fe-O)'s and ΔH homo(Fe-S)'s [ΔΔHhomo(Fe-O)'s and ΔΔHhomo(Fe-S)'s] can also be satisfactorily predicted. The good correlations [r = 0.98 (g, 1), 0.98 (g, 2)] of ΔΔH homo(Fe-O)'s and ΔΔHhomo(Fe-S)'s in series 1 and 2 with the substituent σp+ constants imply that the para-substituent effects on ΔHhomo(Fe-O)'s and ΔHhomo(Fe-S)'s originate mainly from polar effects, but those on radical stability originate from both spin delocalization and polar effects. ΔΔHhomo(Fe-O)'s (1) and ΔΔH homo(Fe-S)'s (2) conform to the captodative principle. Insight from this work may help the design of more effective catalytic processes. Copyright ? 2013 John Wiley & Sons, Ltd.