Remote substituent effects on homolytic FeC bond energies of p‐G‐C₆H₄CH₂Fe(CO)₂(η⁵‐C₅H₅) and p‐G‐C₆H₄(H)(CN)CFe(CO)₂(η⁵‐C₅H₅) studied by Hartree–Fock and density functional theory methods

Abstract

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., DH homo (Fe-C)s] of 12 para-substituted benzyldicarbonyl(h 5 -cyclopentadienyl)iron, p-G-C 6 H 4 CH 2 Fp [1,G ¼ NO 2 , CN, COMe, CO 2 Me, CF 3 , Br, Cl, F, H, Me, MeO, NMe 2 ; Fp¼ (h 5 -C 5 H 5 )(CO) 2 Fe] and 12 para-substituted a-cyanobenzyldicarbonyl (h 5 -cyclopentadienyl)iron, p-G-PANFp [2,PAN ¼ C 6 H 4 CH(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 DH homo (Fe-C)s. The B3LYP method satisfactorily predicts the a and remote substituent effects on DH homo (Fe-C)s [DDH homo (Fe-C)s]. The fair correlations [r ¼ 0.97 (g, 1), 0.99(g, 2)] of DDH homo (Fe-C)s of series 1 and 2 with the substituent s R p constants imply that the para substituent effects on DH homo (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 DDH homo (Fe-C)s(1) varies significantly but also the direction changes from S-pattern to O-pattern. DDH homo (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.

Hartree–Fock and density functional theory study of remote substituent effects on heterolytic Fe–N bond energies of p‐G‐C6H4NHFe(CO)2(η5‐C5H5) and p‐G‐C6H4N(COMe)Fe(CO)2(η5‐C5H5)

“…The breaking and forming of metal–ligand bonds are recurrent reactions in organometallic chemistry, and accurate estimates of the corresponding bonding energies are essential for the understanding of many processes, ranging from organometallic synthesis to catalysis, surface chemistry, photophysics, and photochemistry . Despite the development of a range of techniques for probing metal–ligand bond energy information, both in solution and in the gas phase, the amassed library of organometallic bond energies remains extremely limited . In the last few years, density functional theory (DFT) has become a very popular computational method for the calculation of a number of molecular properties.…”

“…Thermodynamic studies to so important FpR complexes are notably scarce . In our laboratory, para‐substituted anilinyldicarbonyl(η 5 ‐cyclopentadienyl)iron [ p ‐G‐C 6 H 4 NH(η 5 ‐C 5 H 5 )Fe(CO) 2 , abbreviated as p ‐G‐C 6 H 4 NHFp ( 1 )] and para‐substituted α‐acetylanilinyldicarbonyl(η 5 ‐cyclopentadienyl)iron [ p ‐G‐C 6 H 4 N(COMe)(η 5 ‐C 5 H 5 )Fe(CO) 2 , abbreviated as p ‐G‐C 6 H 4 N(COMe)Fp ( 2 ), where G = NO 2 , CN, COMe, CO 2 Me, CF 3 , Br, Cl, F, H, Me, MeO, and NMe 2 ] complexes were studied as models for the Fp–N bond heterolysis (Fig.…”

Remote substituent effects on homolytic Fe‐N bond energies of p‐G‐C6H4NHFe(CO)2(η5‐C5H5) and p‐G‐C6H4(COMe)NFe(CO)2(η5‐C5H5) studied using Hartree–Fock and density functional theory methods

“…The quantitative understanding of molecular bond energies is one of the “grand quests” in chemistry. Unfortunately, the experimental determination of metal–ligand bond dissociation energy (BDEs) in organometallic complexes is often difficult . Density functional theory (DFT), however, has proven to be a powerful alternative in this effort, especially after the development of nonlocal and hybrid DFT methods.…”

“…However, there are scarce reports on the Fe‐N bond energy in Fp compounds . Methods described by Venimadhavan et al ., Borderwell et al .…”

“…In this article, para‐substituted anilinyldicarbonyl(η 5 ‐cyclopentadienyl)iron [ p ‐G‐C 6 H 4 NH(η 5 ‐C 5 H 5 )Fe(CO) 2 , abbreviated as p ‐G‐C 6 H 4 NHFp ( 1 ), where G=NO 2 , CN, COMe, CO 2 Me, CF 3 , Br, Cl, F, H, Me, MeO and NMe 2 ] and para‐substituted α‐acetylanilinyldicarbonyl(η 5 ‐cyclopentadienyl)iron [ p ‐G‐C 6 H 4 N(COMe)(η 5 ‐C 5 H 5 )Fe(CO) 2 , abbreviated as p ‐G‐C 6 H 4 N(COMe)Fp ( 2 )] complexes were studied as models for the Fp‐N bond homolysis (Fig. ) using ab initio Hartree–Fock (HF) and density functional methods used in previous work …”