•We investigated the mechanisms of iron-catalyzed direct arylation of Iodobenzene with Benzene.•The halogen atom transfer mechanism was favored.•The rate-limiting step for the halogen atom transfer mechanism was the first step to produce the phenyl radical with the energy barrier of ΔE = 29.8 kcal/mol in the gas phase and the Gibbs free energy in solvent benzene ΔGsol = 37.7 kcal/mol.Iron-catalyzed direct arylations of unactivated arenes with aryl iodides provide an important method to form C-C bonds. The present study explored the mechanisms of iron(II)-catalyzed direct arylation of Iodobenzene with Benzene using Density Functional Theory (DFT) calculations at the B3LYP-D3 level, which included the halogen atom transfer (to produce aryl radical) mechanism, the single electron transfer mechanism, the σ–bond metathesis mechanism and the oxidative addition mechanism. The calculated results showed that the halogen atom transfer mechanism was favored. The rate-limiting step for the halogen atom transfer mechanism was the first step to produce the phenyl radical with the energy barrier of ΔE = 29.8 kcal/mol in the gas phase and the Gibbs free energy in solvent benzene ΔGsol = 37.7 kcal/mol. The substituent effects of phenyl iodide were also studied.The mechanisms of iron-catalyzed direct arylation of Iodobenzene with Benzene were studied using DFT calculations. The results showed that halogen atom transfer mechanism was favored where the rate-limiting step was the first step to produce phenyl radical with the energy barrier of ΔE = 29.8 kcal/mol and ΔGsol = 37.7 kcal/mol.Download high-res image (56KB)Download full-size image

•We studied the electronic properties of M-doped (M = B, C, N, Mg, Al) VO2 using DFT calculations.•The band gaps of Eg2 for all M-doped VO2 were smaller than that of pure VO2.•The C-doped VO2 could be the best one for achieving good thermochromic energy-saving performance.Models for M-doped (M = B, C, N at O site, and M = B, Mg, Al at V site) VO2 (M1 phase) were studied using the first-principles density functional theory electronic structure calculations to evaluate the effect of M (M = B, C, N, Mg, Al) doping on the band edges. Our results showed that the band gaps of Eg2 for all M-doped VO2 were smaller than that of pure VO2 (M1 phase, 0.78 eV). The band gap of Eg2 for C-doped VO2 was the smallest (0.434 eV), which can be concluded that the C-doped VO2 could be the best one for achieving good thermochromic energy-saving performance from the electronic properties. These findings will provide a new routine of modulating the phase transition of VO2 for the experimental works.The electronic properties of M-doped (M = B, C, N at O site, and M = B, Mg, Al at V site) VO2 (M1 phase) were studied using DFT calculations. Our results showed that the C-doped VO2 could be the best one for achieving good thermochromic energy-saving performance.

The mechanisms of highly regioselective iron(II)-catalyzed synthesis of α-carboxylic acids from alkene derivatives and CO2 have been investigated using density functional theory (DFT) calculations at the B3LYP-D3 level. The results show that the overall catalytic cycle includes β-hydride elimination, hydrometalation, oxidative addition of EtMgBr, reductive elimination, and carboxylation using CO2. However, the first and second steps could be replaced by a favored concerted one-step mechanism without forming the iron hydride complex. The rate-limiting step for the whole catalytic cycle is the reductive elimination step, where the energy barrier ΔE is 37.3 kcal/mol in the gas phase and the Gibbs free energy in solvent THF ΔGsol is 30.3 kcal/mol, computed using the SMD method. The mechanisms to obtain the byproduct β-carboxylic acids are also studied.

The mechanisms of iron(II) bromide-catalyzed intramolecular C–H bond amination [1,2]-shift tandem reactions of aryl azides have been studied using density functional theory calculations. The tandem reaction from R1, 1-azido-2-(1-methoxy-2-methylpropan-2-yl)benzene, to produce P2, 2,3-dimethyl-1H-indole, was calculated. Our results showed that the overall catalytic cycle includes the following steps: (I) extrusion of N2 to form iron nitrene; (II) C–H bond amination; (III) formation of the middle product P1, 2-methoxy-3,3-dimethylindoline; (IV) iminium ion formation ; (V) [1,2]-shift process; and (VI) formation of indole P2. The rate-limiting step is the [1,2]-shift process, where the energy barrier ΔE = 28.7 kcal/mol in the gas phase. Our calculated results also indicated that the preference for the [1,2]-shift component of the tandem reaction is methyl < ethyl.

•We investigated mechanisms of formation of biphenyl in Ni-catalyzed reductive cross-coupling system.•The triplet Ni0 mechanism is more favored than the singlet Ni0 mechanism and the NiI mechanism.•The rate-limiting step is the second oxidative addition step (NiI → NiIII).•We studied ligand effects of four kinds of different bipyridine style ligands.The mechanisms of formation of biphenyl in Ni-catalyzed reductive cross-coupling system have been studied using Density Functional Theory calculations. Our calculated results showed that the triplet Ni0 mechanism is more favored than the singlet Ni0 mechanism and the NiI mechanism. The overall catalytic cycle of the favored Ni0 mechanism includes the following basic steps: 1. First oxidative addition (Ni0 → NiII); 2. Reduction (NiII → NiI); 3. Second oxidative addition (NiI → NiIII); 4. Reductive elimination (NiIII → NiI); 5. Catalyst regeneration (NiI → Ni0). The rate-limiting step for the whole catalytic cycle is the second oxidative addition step (NiI → NiIII), where the electronic energy barrier ΔE is 11.91 kcal/mol in the gas phase and the Gibbs free energy in solvent CH3CN ΔGsol is 14.38 kcal/mol computed using the C-PCM method. Our calculated results also indicated that different functional groups in bipyridine style ligands have little effect on the homocoupling mechanisms.The mechanisms of formation of biphenyl in Ni0 or NiI-catalyzed reductive cross-coupling system have been studied using DFT calculations. Bromobenzene was used as the substrate. Our calculated results showed that the triplet Ni0 mechanism is more favored than the singlet Ni0 mechanism and the NiI mechanism.

Experimental studies recently show that iron salts are effective catalysts for oxaziridine-mediated oxyamination reactions, in place of the powerful osmium-catalyzed Sharpless aminohydroxylation method. The present study reports a theoretical analysis of the mechanism of the iron-catalyzed aminohydroxylation reaction between vinylbenzene and N-sulfonyloxaziridine substrate using density functional theory (DFT) calculations. Our calculations show that the Fe(II)-catalyzed process is favored over the Fe(III)-catalyzed process for the overall catalytic cycle. The rate-limiting step in the whole catalytic cycle is the process of forming the final aminohydroxylation product from a six-membered-ring intermediate, but the solvation effect in MeCN of this step leads to a lowering of the energy barrier computed using the C-PCM method. The regioselectivity has also been investigated.

First-principles density functional theory (DFT) electronic structure calculations were carried out for the model halogen-doped VO2 (M1 phase) to evaluate the effect of halogen (X = F, Cl, Br, I) doping on the band edges. The model structures of X-doped VO2 with X at V site or O site were constructed on the basis of 96-atom 2 × 2 × 2 supercell of monoclinic M1 phase of VO2. Our results showed that the band gap Eg2 for Cl-doped VO2 at O1 site (0.51 eV) is smaller than that of F-doped VO2 at O1 site (0.61 eV) and that of pure VO2 (0.78 eV). We also investigated the substitution of chlorine, bromine, and iodine for vanadium in VO2, where the band gaps Eg2 are 0.40, 0.45, and 0.37 eV for Cl-, Br-, and I-doped VO2 at V site, respectively. The Cl-doped VO2 at V site is the best one for achieving good VO2 thermochromic energy-saving foils.

When compared with the established palladium and nickel catalyst systems, simple iron salts turn out to be highly efficient, cheap, toxicologically benign, and environmentally friendly precatalysts for a host of cross-coupling reactions of alkyl or aryl Grignard reagents. The inorganic Grignard reagent [Fe(MgX)2], where X corresponds to Br or I, is a good catalyst for cross-coupling reactions. The present study reports a thorough theoretical analysis of the mechanisms of the [Fe(MgBr)2] catalyzed cross-coupling reaction between 4-chlorobenzoic acid methyl ester and n-hexylicmagnesium bromide using density functional theory (DFT) calculations. Our calculations show that the overall catalytic cycle includes three basic steps: oxidation of [Fe(MgBr)2] to obtain [Ar–Fe(MgBr)], addition to yield [Ar–(n-hexyl)–Fe(MgBr)2], and reductive elimination to return to [Fe(MgBr)2]. The energy barrier is lower if n-hexylicmagnesium bromide attacks the intermediate of the oxidative addition directly before [Cl–Mg–Br] dissociates to form the middle product [Ar–Fe(MgBr)] than if the attack occurs after the dissociation of [Cl–Mg–Br]. The solvation effect in this step clearly leads to a lowering of the energy barrier. The rate-limiting step in the whole catalytic cycle is the reductive elimination of [Ar–(n-hexyl)–Fe(MgBr)2] to regenerate the catalyst [Fe(MgBr)2], where the electronic energy barrier ΔE is 29.74 kcal/mol in the gas phase and the Gibb’s free energy in solvent THF ΔGsol is 28.13 kcal/mol computed using the C-PCM method.

The present work highlights unprecedented Ni-catalyzed reductive coupling of unactivated alkyl iodides with aryl acid chlorides to efficiently generate alkyl aryl ketones under mild conditions.