Yuri F. Oprunenko

Regioselective synthesis of π-complexes of substituted polycyclic aromatic compounds. Experimental (NMR) and theoretical (DFT) studies of η6,η6-haptotropic rearrangements in naphthalenechromiumtricarbonyl complexes☆

A new regioselective method for the synthesis of (η6-naphthalene)chromium tricarbonyl complexes bearing a substituent R in desired positions of either the coordinated or non-coordinated ring was proposed. The kinetics of η6,η6-haptotropic rearrangements (IRHR) was investigated by NMR spectroscopy for ten pairs of isomer complexes (R=D, CH3, Me3Sn, Me3Si and Cl in position 1 or 2 of coordinated or non-coordinated rings). The free activation energies ΔG# fall into a quite narrow range of 28–31 kcal mol−1 and are therefore relatively insensitive to the influence of substituent R whereas equilibrium constants of IRHR change considerably from 0.03 to 17.26 within the compounds investigated. Electron donating (withdrawing) substituents R increase (decrease) the relative thermodynamic stability of the isomers containing a substituent in coordinated rings. The density functional theory method (DFT) with extensive basis set describes quite satisfactory the geometry and the energy of ground states and correctly predict that the least motion route of Cr(CO)3 from one ring to another via the center of the C4a–C8a bond is forbidden. The transition state for the rearrangement of (η6-naphthalene)chromium tricarbonyl has trimethylenemethane structure of C2v-symmetry in which the Cr(CO)3-group is slightly shifted to the ligand periphery. For the monosubstituted naphthalenechromium tricarbonyls thus, there are two reaction channels of the chromium tricarbonyl group slippage between unsubstituted and substituted rings, one of which is practically unperturbed determining the low sensitivity of the rearrangement rate to the effects of ligand substitution even for 1-R substituted complexes. Calculated activation barriers are in a good accordance with the experimentally determined ΔG# values.

Intramolecular versus intermolecular mechanism of metallotropic rearrangements of chiral chromium tricarbonyl complexes of substituted naphthalenes and other polyaromatic compounds investigated by chiral HPLC of its racemic mixtures

Abstract Pure enantiomers of chromium tricarbonyl complexes of α- and β-monosubstuted naphthalenes RC 10 H 7 Cr(CO) 3 (R=Cl, Me, SiMe 3 , SnMe 3 ) were separated as pure enantiomers by chiral phase HPLC on a Chiracel OD column. Inter-ring haptotropic rearrangements (IRHRs) (process in which metal shifts between substituted and non-substituted rings) of pure enantiomers were investigated in different solvents in the presence or absence of some solvating additives. It was shown that IRHR proceeds at 85°C in noncoordinative and noncomplexing solvents such as hexafluorobenzene or decane through an intermolecular mechanism without racemization. In aromatic toluene, which can bind with the organometallic group, it proceeds through a partially intramolecular mechanism, leading to considerable racemization (ca. 20%) of the complexes. In the presence of solvating additives (THF, dibutyl ether), almost complete racemization (>90%) was observed.

Redox-induced activation of CH bonds in 1,2,3,4,5-pentamethylcyclopentadiene platinum complexes

The electrochemical behaviour of the platinum complexes [Pt(η4C5Me5H)(η5C5H5)] +BF4− (1+) and [Pt(η4-diene)(η5C5Me5)]+BF4− (diene = C5Me5H (2+) or 1,3-cyclohexadiene; (3+) 1,5-cyclooctadiene(4+)) has been studied by cyclic voltammetry. The complexes 1+−4+ are capable of both oxidation and reduction. The bulk electrolysis of 2+ at the potential of its reduction gives a mixture of twe neutral isomeric complexes 5a and 5b. These are assigned structures with η3-allylic and of σ, π-bonding methylene cyclopentenyl Me3C5H(CH2) ligand. This is the proposed result from methyl CH bond breakage in pentamethylcyclopentadiene ligand of an intermediate 19-electron complex [Pt(η4C5Me5H) (η5C5Me5)]. (2.). The same mixture of isomers 5a and 5b forms in interaction of 2+ and tBuOK in tetrahydrofuran. The preparative electrochemical oxidation of 2+ proceeds with CH bond scission at the pentamethylcyclopentadiene sp3-hydridized carbon in an intermediate 17-electron dication radical [Pt(η4C5Me5H)(η5C5Me5)].2+ (2.2+) to give decamethylplatinacene dication [Pt(η5C5Me5)2]2+(BF4−)2 (72+). The one-electron reduction of 72+ regenerates 2+.

Synthesis and reduction of trifluoromethyl-substituted arenecyclopentadienylruthenium sandwiches [Ru(η5-C5Me4CF3)(η6-C6R6)]+ (R=H, Me) and [Ru(η5-C5Me5)(η6-C6H5CF3)]+

Abstract Dimer [Ru 2 ( η 5 -C 5 Me 4 CF 3 ) 2 Cl 2 ( μ -Cl) 2 ] ( 1 ) has been prepared by reaction of RuCl 3 ·(H 2 O) 3 with 1,2,3,4-tetramethyl-5-(trifluoromethyl)cyclopentadiene in ethanol under reflux. Cationic arenecyclopentadienyl complexes [Ru( η 5 -C 5 Me 4 CF 3 )( η 6 -arene)] + PF 6 − ( 2 + , arene=C 6 H 6 ; 3 + , arene=C 6 Me 6 ) and [Ru( η 5 -C 5 Me 5 )( η 6 -C 6 H 5 CF 3 )] + BF 4 − ( 4 + ) were obtained by refluxing [Ru 2 ( η 5 -C 5 Me 4 CF 3 ) 2 Cl 2 ( μ -Cl) 2 ] ( 1 ) or [Ru 2 ( η 5 -C 5 Me 5 ) 2 Cl 2 ( μ -Cl) 2 ] with corresponding arenes in alcohol. The redox properties of 2 + – 4 + were studied by cyclic voltammetry (CV). All three complexes 2 + – 4 + are reduced irreversibly in one-electron process. The values of reduction peak potentials for 2 + – 3 + are less negative than those found for η 5 -C 5 Me 5 analogues. The reduction of 2 + and 3 + with sodium amalgam in tetrahydrofuran led to the formation of dimers [Ru 2 ( η 5 -C 5 Me 4 CF 3 ) 2 ( μ – η 5 : η 5 -C 6 H 6 C 6 H 6 )] ( 5 ) and [Ru 2 ( η 5 -C 5 Me 4 CF 3 ) 2 ( μ – η 5 : η 5 -C 6 Me 6 C 6 Me 6 )] ( 6 ) respectively. The reduction of 4 + gave a non-identifiable mixture of neutral products.

Reaction of digermanes and related Ge-Si compounds with trifluoromethanesulfonic acid: synthesis of helpful building blocks for the preparation of Ge-Ge(Si)-catenated compounds

Abstract The reaction of a series of compounds, Ar3 Ge-MR3, 1–4 (Ar=Ph, p-Tol, M=Si, Ge, R=Ph, Me, tBu), with one equivalent of trifluoromethanesulfonic acid (HOTf) was investigated. The corresponding triflates were isolated in several cases. The molecular structure of Ph3 Ge-GePh2 OTf (5) in solid state was investigated by X-ray analysis. The triflates were converted to the corresponding chlorides under the action of ammonium chloride.

Molecular Oligogermanes and Related Compounds: Structure, Optical and Semiconductor Properties

The optical (UV/Vis absorbance, fluorescence in the solid state and in solution) and semiconducting properties of a number of di- and trigermanes as well as related silicon- and tin-containing germanes, 1-6 ((p-Tol)3 GeGeMe3 (1), Ph3 SnGe(SiMe3 )3 (2), (C6 F5 )3 GeGePh3 (3), (p-Tol)3 GeSiMe2 SiMe3 (4), (p-Tol)3 GeGeMe2 Ge(p-Tol)3 (5), (p-Tol)3 GeSiMe2 SiMe2 Ge(p-Tol)3 (6)) were investigated. Molecular structures of 5 and 6 were studied by X-ray diffraction analysis. All compounds displayed luminescence properties. In addition, a band gap (of about 3.3 eV) was measured for compounds 1-6 showing that those molecules display semiconductor properties.

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 1505509: Experimental Crystal Structure Determination

Related Article: Kirill V. Zaitsev, Kevin Lam, Zhaisan Zhanabil, Yerlan Suleimen, Anastasia V. Kharcheva, Viktor A. Tafeenko, Yuri F. Oprunenko, Oleg Kh. Poleshchuk, Elmira Kh. Lermontova, and Andrei V. Churakov|2017|Organometallics|36|298|doi:10.1021/acs.organomet.6b00767

N,O-ditosylethanolamine as effective reagent for the synthesis of heterocyclic tertiary amine salts

ABSTRACT During the synthesis of N-tosylaziridine, two unexpected products were isolated: 1-(2-(p-tolylsulfonamido)ethyl)pyridinium p-tolylsulfonate (3) and N,N,O-tri-(p-tolylsulfonyl)ethanolamine (3a). The structures of 3 and 3a were investigated in solid state by X-ray analysis. A new family of related salts was obtained using an efficient and facile one-pot synthesis consisting in the interaction between various nitrogen heterocycles and N,O-ditosylethanolamine. GRAPHICAL ABSTRACT

Synthesis and crystal structure of the germatrane E-N(CH)2CH2O3GeC(Br)=C(Br)Ph

The reaction of (phenylacetylenyl)triethoxygermane, (EtO)3GeC≡CPh (3), with bromine in CHCl3/CCl4 solution leads to a mixture of Z- and E- (EtO)3GeC(Br)=C(Br)Ph (4) in the ratio Z/E = 3/1. Treatment of this product with N(CH2CH2OH)3 affords a mixture of Z- and EN(CH2CH2O)3GeC(Br)=C(Br)Ph (2) in high yield. Compound E-2 was isolated in 16% yield. The molecular composition and the structure of all new compounds have been established by elemental analyses, 1H and 13C NMR spectroscopy. The crystal structure of E-2 is reported. The possible reasons for the different Z/E ratios in the products of the bromination of 3 and N(CH2CH2O)3GeC≡CPh (1) are discussed using DFT calculations.