A computational study of the succinimide derivative surfactant

Density functional theory (DFT) of calculations was used to optimize the molecular structures of a succinimide surfactant at B3LYP/6-311 level. The interaction of the surfactant with water molecules was investigated. The hydration shell was formed in the form of Hbonds between the hydrophilic group on the surfactant and water molecules. The binding energy of the system increases due to hydrogen bond formation with the water molecules.http://www.tandfonline.com/loi/ldis20hb2013ai201

Mo Fischer carbene complexes : a DFT study on the prediction of redox potentials

Please read abstract in the article.The University of the Free State; the National Research Foundation (NRF) in South Africa; the High-Performance Computing facility of the UFS, the Centre for High-Performance Computing (CHPC) of South Africa and the Norwegian Supercomputing Program.https://iopscience.iop.org/journal/1945-7111hj2022Chemistr

Multidentate NHC complexes of group IX metals featuring carbon-based tethers : synthesis and applications

Incorporation of N-tethers to N-heterocyclic carbene ligands to form a powerful class of multidentate, responsive ligand frameworks that have proven to be more than just ancillary ligands with reported success and usefulness in a multitude of applications. NHC complexes of group IX transition metals (Co, Rh, Ir) have enjoyed considerable research interest over the last two decades, owing to their vast range of accessible oxidation states, favourable stabilities and reactivities, as well as multi-functional use. The inclusion of carbon as a secondary binding atom has been extremely useful to help enable the resulting metal complex for complex C–H activation, small molecule fixation and activation, and unusual migratory insertion reactions. This comprehensive review communicates results that demonstrate the versatility of this carbon-based multidentate ligand series through inclusion of synthetic routes available to access the metal-NHC complexes, their associated stability and reactivity pathways, as well as advances made in several different applications, most notably homogeneous catalysis.The South African National Research Foundation and the University of Pretoria.http://www.elsevier.com/locate/ccrhj2022Chemistr

Conformational preferences of heteronuclear Fischer carbene complexes of cymantrene and cyclopentadienyl rhenium tricarbonyl

Homo- and heteronuclear bimetallic carbene complexes of group VII transition metals (Mn and Re), with cymantrene or cyclopentadienyl rhenium tricarbonyl as the starting synthon, have been synthesized according to classic Fischer methodology. Crystal structures of the carbene complexes with general formula [RC5 H4  M'(CO)2 {C(OEt)(C5 H4  M(CO)3 )}], where M = M′ = Mn, R = H (1), R = Me (2); M = Mn, M′ = Re, R = H (3); M = M′ = Re, R = H (4); and M = Re, M′ = Mn, R = H (5), are reported. A density functional theory (DFT) study was undertaken to determine natural bonding orbitals (NBOs) and conformational as well as isomeric aspects of the binuclear complexes. Application of second-order perturbation theory (SOPT) of the NBO method revealed stabilizing interactions between the methylene C–H bonds and the carbonyl ligands of the carbene metal moiety. Energy calculations in the gas phase of the cis and trans conformations of the Cp rings relative to one another are comparable, with the trans conformation slightly lower in energy. The theoretical findings have also been confirmed with single-crystal X-ray diffraction, and all solid-state structures are found in the trans geometry.The South African National Research Foundation [grant number 93638] and the University of Pretoria.http://www.tandfonline.com/loi/gcoo202017-09-30hb2016Chemistr

Electrochemical study of chromium(0) Fischer carbene complexes : trends in redox potential

It is illustrated that the electrochemical redox potentials of chromium(0) Fischer carbene complexes containing a heteroaromatic substituent can be determined to a high degree of accuracy from the gas phase density functional theory (DFT) optimized frontier orbital energies, with a mean average error of the calculated redox potentials of 0.047 V for the chromium-based oxidation potential and 0.057 V for the carbene ligand based reduction potential. For the first time it was possible to distinguish between the Cr0/I oxidation peaks of the E and the Z-isomer of a cyclohexylamino pentacarbonyl chromium Fischer carbene complex, namely [(CO)5CrC(NHCy)(2-thienyl)]. The linear relationship obtained between the oxidation potential and the DFT calculated highest molecular orbital energies, made it possible to assign the oxidation peak at the lower less positive oxidation potential to the oxidation of the E isomer, and the peak at the slightly higher (more positive) oxidation potential to the oxidation of the Z isomer of [(CO)5CrC(NHCy)(2-thienyl)].The South African National Research Foundation (JC, ML), the Central Research Fund of the University of the Free State, Bloemfontein, South Africa (JC, EE) and the University of Pretoria, Pretoria, South Africa (ML).http://www.elsevier.com/locate/poly2018-05-08Chemistr

Synthesis and XPS characterization of Si-supported chromium(0) Fischer aminocarbene complexes

Ethoxy chromium (0) Fischer carbene pentacarbonyl complexes [(CO)5CrC(OEt)R]; R = 2- thienyl (1), 2-furyl (2) were covalently anchored onto aminopropyltrimethoxysilanefunctionalised silicon-wafers to form Cr-grafted Si-wafers S1 and S2 that were characterized by X-ray photoelectron spectroscopy (XPS). X-ray photoelectron spectroscopy determined that binding energy of the Cr 2p3/2 photoelectron line of the thienyl-containing complexes were smaller than that of the furyl-containing complexes. The binding energy of the Cr 2p3/2 photoelectron line of the ethoxycarbene complexes was smaller than that of aminocarbenes. The binding energy of the Cr 2p3/2 photoelectron line of the Cr-grafted Si-wafers were ca. 1 eV higher than that of the related aminocarbenes. A 25 – 33 % anchoring of the Crcomplexes 1 and 2 on the aminopropyltrimethoxysilane-functionalised silicon-wafers was achieved.The South African National Research Foundation (JC, ML), the Central Research Fund of the University of the Free State, Bloemfontein, South Africa (JC, EE) and the University of Pretoria, Pretoria, South Africa (ML).http://www.elsevier.com/locate/jorganchem2018-05-31hb2017Chemistr

Electrochemistry of Fischer alkoxycarbene complexes of chromium : the use of Density Functional Theory to predict and understand oxidation and reduction potentials

The electrochemical behaviour of a series of Fischer ethoxycarbene complexes of the type [(CO)5Crdouble bond; length as m-dashC(OEt)R] with R = 2-thienyl (1), 2-furyl (2), 2-(N-methylpyrrolyl) (3), N-methyl-2-(2′-thienyl)pyrrole) (4) and 2,2′-thienylfuran (5), is investigated by means of cyclic voltammetry. Results show that the first one electron reduction process is sensitive to the energy, shape and distribution of the LUMO orbital, leading to a linear relationship between the formal reduction potential and the LUMO energy: E0′(Ccarbene) = –0.70 ELUMO–3.44 (R2 = 1.00) which is valid over a large potential range. The dimeric heteroarene substituents of 4 and 5 lead to enhanced stabilization of the reduced complexes 4 and 5, making another one electron reduction possible. The formal reduction potential, E0′(Cr) of the first oxidation process of 1–5 lays within a narrow potential range of 0.43–0.50 V vs. Fc/Fc+, is Cr-based and is mainly sensitive to the electrophilic character of the heteroarene ring directly attached to the carbene carbon.http:// www.elsevier.com/locate/electactahb2014ai201

Facile Suzuki-Miyaura coupling of activated aryl halides using new CpNiBr(NHC) complexes

Nine new Ni(II)-NHC complexes, [CpNiBr(NHC)], were synthesised from nickelocene and the corresponding symmetric or asymmetric alkyl/-benzyl/phenylethyl imidazolium bromide ligands in relatively high yield. Access to each of the synthesised symmetric or asymmetric alkyl/benzyl/phenylethyl imidazolium bromide salts was obtained through deprotonation of imidazole, followed by treatment with an alkyl- or aryl halide, which is subsequently followed with reaction of a secondary alkyl-, benzyl-, or phenylethyl halide. The series of [CpNiBr(NHC)] exhibited catalytic activity in the Suzuki-Miyaura coupling of activated aryl halides with phenylboronic acid to give the respective biphenyl and biphenyl-containing products. In general, the more electron-donating NHC-bearing Ni complexes showed higher activity with aryl halides bearing electron-withdrawing functionalities including carboxaldehyde moieties. All complexes were characterised by 1H- and 13C-NMR spectroscopy, FT-IR spectroscopy, CHN and MS analyses, along with six selected single crystal X-ray structures that are reported here.The National Research Foundation of South Africa (NRF) and the University of Pretoria (UP).http://www.elsevier.com/locate/jorganchem2017-07-31hb2016Chemistr

Conformation analysis of triphenylphosphine in trans and cis triphenylphosphine-substituted Fischer carbene complexes

The synthesis and selected crystal structures of novel (M = Cr or Mo) and known (M =W) [(CO)4(PPh3) M = C(OEt)R] complexes, M = Cr, R = 2-thienyl (1), 2-furyl (2); M = Mo, R = 2-thienyl (3), 2-furyl (4); M = W, R = 2-thienyl (5), 2-furyl (6), are presented. Experimental crystal structures and DFT calculations of selected trans- and cis-triphenylphosphine-substituted Fischer carbene complexes, illustrate that the minimum energy conformation of triphenylphosphine (PPh3) in octahedral [(CO)4(PPh3)ML]-complexes generally have distinct features that can be described in terms of the ‘‘plane of nadir energy’’, a plane linking all points of minimum steric compression between the ligands. The generally observed orientation of PPh3 involves a correlated feathering of the phenyl groups with the PACipso bond of one phenyl group orientated near parallel to the nadir plane, and a meta carbon (Cm) of the other two phenyl groups orientated as near as possible to the nadir plane, orthogonal to the first. Although the orientation of PPh3 in 6-trans, [(CO)4(PPh3)W = C(OEt)2-furyl], deviates from this, DFT correctly calculated the unexpected and not generally observed PPh3 orientation.South African National Research Foundation, the Central Research Fund of the University of the Free State (JC) and the University of Pretoria.http://www.elsevier.com/locate/molstruchb201

Conformation of a MnCP(CO)2-thienothiophene carbene complex : a spectroscopic and computational study

The carbine complex [MnCp(CO)2C(OEt)(TT)], (TT = 3,6-dimethylthieno[3,2-b]thiophene) 1, was synthesized according to the classical Fisher method. The novel complex was fully characterized using various spectroscopic techniques. The infrared spectrum of the complex, recorded as a solution in dichloromethane, revealed a four-band spectrum in the carbonyl region instead of the expected two-band spectrum. A density functional theory (DFT) study was undertaken to explain the presence of more than one conformer in solution. The crystal structure of 1 is reported.http://www.elsevier.com/locate/molstru