Search

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. [ABSTRACT FROM AUTHOR]

The thermochemistry of organometallic complexes in solution and in the gas phase has been an area of increasing research interest. In this paper, the Fe-O and Fe-S homolytic bond dissociation energies [ΔHhomo(Fe-O)'s and ΔHhomo(Fe-S)'s] of two series of meta-substituted phenoxydicarbonyl(η5-cyclopentadienyl) iron [m-G-C6H4OFp (1)] and (meta-substituted benzenethiolato)dicarbonyl(η5-cyclopentadienyl) iron [m-G-C6H4SFp (2)] were studied using Hartree-Fock and density functional theory 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 Tao-Perdew-Staroverov-Scuseria and Minnesota 2006 functionals can provide the best price/performance ratio and accurate predictions of ΔHhomo(Fe-O)'s and ΔHhomo(Fe-S)'s. The polar effects of the meta substituents show that the dominant role to the magnitudes of ΔΔHhomo(Fe-O)'s or ΔΔHhomo(Fe-S)'s. sa·, sc· values for meta substituents are all related to polar effects. Spin-delocalization effects of the meta substituents in ΔΔHhomo(Fe-O)'s and ΔΔHhomo(Fe-S)'s are small but not necessarily zero. Molecular effects rather than ΔΔHhomo(Fe-O)'s and ΔΔHhomo(Fe-S)'s are more suitable indexes for the overall substituent effects on ΔHhomo(Fe-O)'s and ΔHhomo(Fe-S)'s. The meta substituent effects of meta-electron-withdrawing groups on the Fe-S bonds are much stronger than those on the Fe-O bonds. For meta-electron-donating groups, the meta substituent effects have the comparable magnitudes between series 1 and 2. ΔΔHhomo(Fe-O)'s (1) and ΔΔHhomo(Fe-S)'s (2) conform to the captodative principle. Insight from this work may help the design of more effective catalytic processes. [ABSTRACT FROM AUTHOR]

Metal-ligand bond enthalpy data can afford invaluable insights into important reaction patterns in organometallic chemistry and . In this paper, the Fe-O and Fe-S homolytic bond dissociation energies [Δ Hhomo(Fe-O)'s and Δ Hhomo(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-C6H4SFp ( 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 Δ Hhomo(Fe-O)'s and Δ Hhomo(Fe-S)'s. The remote substituent effects on Δ Hhomo(Fe-O)'s and Δ Hhomo(Fe-S)'s [ΔΔ Hhomo(Fe-O)'s and ΔΔ Hhomo(Fe-S)'s] can also be satisfactorily predicted. The good correlations [ r = 0.98 (g, 1), 0.98 (g, 2)] of ΔΔ Hhomo(Fe-O)'s and ΔΔ Hhomo(Fe-S)'s in series 1 and 2 with the substituent σp+ constants imply that the para-substituent effects on Δ Hhomo(Fe-O)'s and Δ Hhomo(Fe-S)'s originate mainly from polar effects, but those on radical stability originate from both spin delocalization and polar effects. ΔΔ Hhomo(Fe-O)'s ( 1) and ΔΔ Hhomo(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. [ABSTRACT FROM AUTHOR]

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 [ΔHhomo(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 Hartree-Fock (HF) and the density functional theory methods with large basis sets. In this study, Fp is (η5-C5H5)Fe(CO)2 and G are N02, 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 ΔHhomo(Fe-N)'s. B3LYP can also satisfactorily predict the ɑ and remote substituent effects on AHhomo(Fe-N)'s [ΔΔHhomo(Fe-N)'s). The good correlations [r= 0.96 (g, 1), 0.99(g, 2)] of ΔΔHhomo(Fe-N)'s in series 1 and 2 with the substituent σp+ constants imply that the para-substituent effects on ΔHhomo(Fe-N)'s originate mainly from polar effects, but those on radical stability originate from both spin derealization and polar effects. ΔΔHhomo(Fe-N)'s(1,2) conform to the captodative principle. Insight from this work may help the design of more effective catalytic processes. [ABSTRACT FROM AUTHOR]

In general, both stoichiometric and catalytic reactions of organometallic complexes involve breaking and forming metal-ligand bonds. Therefore, an evaluation of the thermodynamics of such reactions requires the knowledge of metal-ligand bond energies (BDEs). The homolytic FeC bond dissociation energies [i.e., Δ Hhomo(FeC)s] of 12 para-substituted benzyldicarbonyl( η5-cyclopentadienyl)iron, p-G-C6H4CH2Fp [1,G = NO2, CN, COMe, CO2Me, CF3, Br, Cl, F, H, Me, MeO, NMe2; Fp = ( η5-C5H5)(CO)2Fe] and 12 para-substituted α-cyanobenzyldicarbonyl ( η5-cyclopentadienyl)iron, p-G-PANFp [2,PAN = C6H4CH(CN)] were studied using Hartree-Fock (HF) and density functional theory (DFT) methods with large basis sets. The results show that BP86 and TPSSTPSS can provide the best price/performance ratio and more accurate predictions in the study of Δ Hhomo(FeC)s. The B3LYP method satisfactorily predicts the α and remote substituent effects on Δ Hhomo(FeC)s [ΔΔ Hhomo(FeC)s]. The fair correlations [ r = 0.97 (g, 1), 0.99(g, 2)] of ΔΔ Hhomo(FeC)s of series 1 and 2 with the substituent σ constants imply that the para substituent effects on Δ Hhomo(FeC)s originate mainly from polar effects, but those on radical stability originate from both spin delocalization and polar effects. The molecule stabilization effects (MEs) causes that not only the magnitude of ΔΔ Hhomo(FeC)s(1) varies significantly but also the direction changes from S-pattern to O-pattern. ΔΔ Hhomo(FeC)s(2) were found to conform to the Capto-dative Principle. The detailed knowledge of the factors that determine the FpC bond strengths would greatly aid in understanding reactivity patterns in many processes. Copyright © 2010 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]