Hartree–Fock and density functional theory study of remote substituent effects on gas‐phase heterolytic Fe–O and Fe–S bond energies of p‐G‐C6H4OFe(CO)2(η5‐C5H5) and p‐G‐C6H4SFe(CO)2(η5‐C5H5) |
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Authors: | Qing Zeng Zucheng Li Daxiong Han Ling Dong Huaqiang Zhai Bin Liu Genben Bai Yujie Zhang |
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Institution: | 1. School of Chinese Pharmacy, Beijing University of Chinese Medicine, , Beijing, 100102 China;2. The State Key Laboratory of Elemento‐organic Chemistry, Nankai University, , Tianjin, 300071 China;3. Department of Geological Sciences, University of Saskatchewan, , Saskatoon, SK S7N 5E2 Canada;4. The Key Laboratory for Chemical Biology of Fujian Province, Department of Chemistry, Xiamen University, , Xiamen, 361005 China |
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Abstract: | The knowledge of accurate bond strengths is a fundamental basis for a proper analysis of chemical reaction mechanisms. Quantum chemical calculations at different levels of theory have been used to investigate heterolytic Fe–O and Fe–S bond energies of para‐substituted phenoxydicarbonyl(η5‐cyclopentadienyl) iron p‐G‐C6H4O(η5‐C5H5)Fe(CO)2, abbreviated as p‐G‐C6H4OFp ( 1 ), where G = NO2, CN, COMe, CO2Me, CF3, Br, Cl, F, H, Me, MeO, and NMe2] and para‐substituted benzenethiolatodicarbonyl(η5‐cyclopentadienyl) iron p‐G‐C6H4S(η5‐C5H5)Fe(CO)2, abbreviated as p‐G‐C6H4SFp ( 2 )] complexes. The results show that BP86 and TPSSTPSS can provide the best price/performance ratio and more accurate predictions in the study of ΔHhet(Fe–O)'s and ΔHhet(Fe–S)'s. The excellent linear free‐energy relations r = 0.99 (g, 1a), 1.00 (g, 2b)] among the ΔΔHhet (Fe–O)'s and Δpka's of O–H bonds of p‐G‐C6H4OH or ΔΔHhet(Fe‐S)'s and Δpka's of S–H bonds of p‐G‐C6H4SH imply that the governing structural factors for these bond scissions are similar. And the linear correlations r = ?0.99 (g, 1g), ?0.98 (g, 2h)] among the ΔΔHhet (Fe‐O)'s or ΔΔHhet(Fe‐S)'s and the substituent σp? constants show that these correlations are in accordance with Hammett linear free‐energy relationships. The polar effects of these substituents and the basis set effects influence the accuracy of ΔHhet(Fe–O)'s or ΔHhet(Fe–S)'s. ΔΔHhet(Fe–O)'s(g) ( 1 ) and ΔΔHhet(Fe–S)'s(g)( 2 ) follow the Capto‐dative principle. The substituent effects on the Fe–O bonds are much stronger than those on the less polar Fe–S bonds. Insight from this work may help the design of more effective catalytic processes. Copyright © 2013 John Wiley & Sons, Ltd. |
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Keywords: | anion stability density functional theory heterolytic bond dissociation energy organometallic compounds substituent effects |
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