Igor P. Gloriozov

The silafulvene: a potentially stable compound containing a double carbonsilicon bond

Abstract Two conformations of dimethylsilafulvene are calculated via a CNDO/2 procedure. One of them is planar while in the other the CH 3 SiCH 3 plane is perpendicular to the cyclopentadienyl ring plane. The conformation energies differ by 19.8 kcal/mol.

Pyridinedicarboxylic Acid Diamides as Selective Ligands for Extraction and Separation of Trivalent Lanthanides and Actinides: DFT Study

This article presents a general approach to solving the urgent practical problem of separation of 4f-(lanthanides, Ln3+) and 5f-elements (actinides, An3+) very similar in properties based on the DFT quantum-chemical supercomputer simulation of Ln3+ and An3+ complexes with polydentate nitrogen-containing heterocyclic ligands. The method allows to calculate the geometry parameters of ligands and complexes and the metal to ligand binding energies with accuracy, permitting a direct comparison of calculation results with the experimental data, and estimate selectivity factors for separation of Eu3+/Am3+ model pair cations (SFAm/Eu) in extraction experiments on a semi-quantitative level. The applicability of the method and the approach demonstrated by DFT-modeling (nonempirical PBE functional, extended relativistic full-electron basis set) of a large series of diamides of pyridine-2,6-dicarboxylic (dipicolinic) acid (L) with different substituents at the amide nitrogen atoms and in the pyridine cycle, as well as their complexes [LM]3+, (H2O)nM(NO3)3 (n = 3, 4), and LM(NO3)3 (M = Eu, Am). Based on the theoretical analysis a new model is proposed that describes the mechanism of Ln3+ and An3+ extraction in two-phase system highly acidic water solution-organic solvent, according to which the formation of An3+ and Ln3+ complexes occurs at the water/organic interface as a substitution reaction of hydroxonium ion in a cavity of a protonated ligand for the metal cation. Calculation results confirm the experimentally established higher extraction ability of dipicolinic acid diamides containing one aryl and one alkyl substituent at the amide nitrogen atoms compared to the N,N,N′,N′-tetraalkyl diamides (“effect of anomalous aryl strengthening”). Based on the simulation results the structure of the modified ligand L suggested that it should ensure maximum An3+/Ln3separation selectivity in the series of dipicolinic acid diamides.

Tunnel effects in oxidative addition reaction of methane to bare Pd atom

The potential-energy surface has been calculated for oxidative addition of methane to a bare Pd atom by the semiempirical LCAO MO SCF CNDO/S2 technque. Quantum rate constants and values of the kinetic isotope effect have been computed for both the ground and vibrationally excited states of Pd–CH4 and Pd–CD4 reactions using the reaction path Hamiltonian approach with evaluation of the reaction path curvature. Quantum tunnelling has been shown to give the dominant contribution to the cumulative rate constant for the Pd–CH4 reaction at temperatures below 200 K.

A density functional study of intra- and interring haptotropic η2,η2 rearrangements in rhodium, ruthenium, and osmium naphthalene complexes

The density functional theory method was used to perform quantum-chemical modeling of the mechanisms of η2,η2-intraring (Intra-HR) and η2,η2-interring (Inter-HR) haptotropic rearrangements for μ2 complexes of naphthalene with rhodium, ruthenium, and osmium. The structure of transition states and intermediates was studied, and the energy parameters of haptotropic rearrangements in these complexes were determined. We used the PBE functional, the TZV2p three-exponential basis set for valence electrons, and the SBK-JC relativistic pseudopotential for core electrons. η2,η2 Intra-HR was found to occur inside the aromatic ring of η2 naphthalene complexes without going outside it through intermediates and transition states with ηn structures (n = 1, 2). Inter-HR occurred as metal replacements on the periphery of the naphthalene ligand through intermediates and transition states with ηn structures (n = 1, 2, 3) from one ring into another. The calculated activation barriers for η2,μ2 Intra-HR and η2,η2 Inter-HR in the complexes studied closely agree with their experimental values.

Structure of products of H-H and C-H bond activation by Ni atom, Ni2 cluster, and Ni-porphyrin complex of Ni2 cluster

New catalytic systems based on porphyrin complexes of Ni2 cluster and capable of activating C-H and H-H bonds are proposed. DFT calculations showed that a Ni2 cluster can coordinate Ni-porphyrin with a considerable gain in energy. The structures of the products of methane and hydrogen activation were discussed.

Regioselectivity in the reactions of the acetonate ion with electron-deficient arenes

The reactions of the acetonate ion with 1,3-dinitro-5-X-, 1,3-X2-5-nitro- (X = NO2, CN, COOCH3, CONH2, COO–, and H), and 1,3,5-tricyanobenzenes were studied by 1H NMR and electronic absorption spectroscopy and by quantum-chemical methods. The kinetic factor is decisive for the initial attack of the carbanion on the C(2) atom of unsymmetrical arenes. However, σ-adducts in which a nucleophile is added to the C(4) atom are more stable thermodynamically. In the case of 1,3-X2-5-nitrobenzenes (X = CN, COOCH3, or CONH2), the σ-adducts with the acetonate group in para-position to the X group unexpectedly proved to be very stable. The structures of the σ-adducts based on trinitro- and 1,3-dinitro-5-cyanobenzenes were determined by X-ray diffraction analysis. Quantum-chemical calculations (the AM1 and PM3 semiempirical methods and the density functional method) were used to interpret the reaction regioselectivity and the molecular and electronic structures of the σ-adducts.

Unusual reaction of bromoalkyl trifluoromethyl ketones with symmetrically disubstituted ethylenediamines. Theoretic investigation applying methods of density functional and multiparticle perturbation theory МР-2

Mechanism of a multistage reaction between α-bromotrifluoromethylenones and N,N′-dialkylethylenediamines was examined in detail using quantum chemical methods of density functional (non-empirical functional РВЕ, extended split TZp-basis) and multiparticle perturbation theory МР-2, basis 6-311+G(d,p), in the gas phase approximation, and also including solvents molecules (water and 2,2,2-trifluoroethanol). The specific solvation of transition states owing to the hydrogen bonds formation with solvent molecules is the main factor governing the direction of the reaction. Trifluoroethanol forms a strong H-bond with the carbonyl oxygen atom of the trifluoroacetyl group increasing its electrophilicity. It also solvates the departing bromide anion facilitating the occurrence of the SN2-substitution reaction. An essential but less important factor is the ability of trifluoroethanol to play the role of a nucleophilic partner by forming hydrogen bonds at the expense of the unshared electron pair of the hydroxyl oxygen facilitating the proton abstraction from the nitrogen atom of the diamine attacking the carbon atom in the course of SN2-substitution.

DFT study of dihydrogen addition to molybdenum π-heteroaromatic complexes: a prerequisite step for the catalytic hydrodenitrogenation process

The range of molybdenum hydride complexes that are sought to participate in the important catalytic hydrodenitrogenation process (HDN) of nitrogen containing polycyclic aromatic hydrocarbons were evaluated by DFT studies. The previously synthesized stable (η6-quinoline)Mo(PMe3)3 complex 1N, in which molybdenum is bonded to the heterocyclic ring, was chosen as a model. The hydrogenation of the quinone heterocycle, which was postulated as the initial step in the overall HDN reaction, is found to occur via three consecutive steps of the oxidative addition of dihydrogen to Mo in 1N. Successive transfer of hydrogen atoms from the metal to the heterocycle leads to the ultimate formation of the tetrahydrido molybdenum intermediate Mo(PMe3)4H413 and 2,2,3,3-tetrahydroquinoline C9H11N 14. All the involved intermediates and transition states have been fully characterized by DFT. This computational modeling of the hydrogenation of quinoline, as a part of extended HDN catalytic processes, provides a fundamental understanding of such mechanisms.

CCDC 1843930: Experimental Crystal Structure Determination

Related Article: Olga N. Gorunova, Ivan M. Novitskiy, Yuri K. Grishin, Igor P. Gloriozov, Vitaly A. Roznyatovsky, Victor N. Khrustalev, Konstantin A. Kochetkov, Valery V. Dunina|2018|Organometallics|||doi:10.1021/acs.organomet.8b00363

CCDC 1843928: Experimental Crystal Structure Determination

Related Article: Olga N. Gorunova, Ivan M. Novitskiy, Yuri K. Grishin, Igor P. Gloriozov, Vitaly A. Roznyatovsky, Victor N. Khrustalev, Konstantin A. Kochetkov, Valery V. Dunina|2018|Organometallics|||doi:10.1021/acs.organomet.8b00363