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Density functional theory study of substituent effects on gas‐phase heterolytic Fe–O and Fe–S bond energies of m ‐G‐C 6 H 4 OFe(CO) 2 (η 5 ‐C 5 H 5 ) and m ‐G‐C 6 H 4 SFe(CO) 2 (η 5 ‐C 5 H 5 )
Author(s) -
Zeng Qing,
Li Zucheng,
Wang YiBo,
Zhai Huaqiang,
Liu Bin,
Tao Ou,
Dong Ling,
Guan Jun,
Zhang Yujie
Publication year - 2017
Publication title -
journal of physical organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.325
H-Index - 66
eISSN - 1099-1395
pISSN - 0894-3230
DOI - 10.1002/poc.3582
Subject(s) - heterolysis , chemistry , cyclopentadienyl complex , substituent , density functional theory , ansatz , electronegativity , crystallography , bond energy , gas phase , computational chemistry , medicinal chemistry , molecule , catalysis , organic chemistry , physics , quantum mechanics
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 (meta‐substituted phenoxy)dicarbonyl(η 5 ‐cyclopentadienyl) iron [ m ‐G‐C 6 H 4 OFp ( 1 )] and (meta‐substituted benzenethiolato)dicarbonyl(η 5 ‐cyclopentadienyl) iron [ m ‐G‐C 6 H 4 SFp ( 2 )] complexes. In this study, Fp is (η 5 ‐C 5 H 5 )Fe(CO) 2 , and G is NO 2 , CN, COMe, CO 2 Me, CF 3 , Br, Cl, F, H, Me, MeO, and NMe 2 . The results show that Tao–Perdew–Staroverov–Scuseria and Becke's power‐series ansatz from 1997 with dispersion corrections functionals can provide the best price/performance ratio and accurate predictions of Δ H het (Fe–O)'s and Δ H het (Fe–S)'s. The excellent linear free energy relations [ r = 1.00 (g, 1e), 1.00 (g, 2b)] among the ΔΔ H het (Fe–O)'s and δΔ G 0 of OH bonds of m ‐G‐C 6 H 4 OH or ΔΔ H het (Fe–S)'s and Δp K a 's of SH bonds of m ‐G‐C 6 H 4 SH imply that the governing structural factors for these bond scissions are similar. And, the linear correlations [ r = −0.97 (g, 1 g), −0.97 (g, 2 h)] among the ΔΔ H het (Fe–O)'s or ΔΔ H het (Fe–S)'s and the substituent σ m constants show that these correlations are in accordance with Hammett linear free energy relationships. The inductive effects of these substituents and the basis set effects influence the accuracy of Δ H het (Fe–O)'s or Δ H het (Fe–S)'s. The ΔΔ H het (Fe–O)'s(g) (1) and ΔΔ H het (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 © 2016 John Wiley & Sons, Ltd.