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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‐C 6 H 4 OFe(CO) 2 ( η 5 ‐C 5 H 5 ) and p ‐G‐C 6 H 4 SFe(CO) 2 ( η 5 ‐C 5 H 5 )
Author(s) -
Zeng Qing,
Li Zucheng,
Han Daxiong,
Dong Ling,
Zhai Huaqiang,
Liu Bin,
Bai Genben,
Zhang Yujie
Publication year - 2014
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.3252
Subject(s) - heterolysis , chemistry , substituent , cyclopentadienyl complex , density functional theory , basis set , bond energy , electronegativity , crystallography , bond strength , computational chemistry , gas phase , stereochemistry , molecule , catalysis , organic chemistry , adhesive , layer (electronics)
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( η 5 ‐cyclopentadienyl) iron [ p ‐G‐C 6 H 4 O( η 5 ‐C 5 H 5 )Fe(CO) 2 , abbreviated as p ‐G‐C 6 H 4 OFp ( 1 ), where G = NO 2 , CN, COMe, CO 2 Me, CF 3 , Br, Cl, F, H, Me, MeO, and NMe 2 ] and para‐substituted benzenethiolatodicarbonyl( η 5 ‐cyclopentadienyl) iron [ p ‐G‐C 6 H 4 S( η 5 ‐C 5 H 5 )Fe(CO) 2 , abbreviated as p ‐G‐C 6 H 4 SFp ( 2 )] complexes. The results show that BP86 and TPSSTPSS can provide the best price/performance ratio and more accurate predictions in the study of Δ H het (Fe–O)'s and Δ H het (Fe–S)'s. The excellent linear free‐energy relations [ r = 0.99 (g, 1a), 1.00 (g, 2b)] among the ΔΔ H het (Fe–O)'s and Δp k a 's of O–H bonds of p ‐G‐C 6 H 4 OH or ΔΔ H het (Fe‐S)'s and Δp k a 's of S–H bonds of p ‐G‐C 6 H 4 SH 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 ΔΔ H het (Fe‐O)'s or ΔΔ H het (Fe‐S)'s and the substituent σ p − 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 Δ H het (Fe–O)'s or Δ H het (Fe–S)'s. 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 © 2013 John Wiley & Sons, Ltd.