Sergei N. Smirnov

Saint Petersburg State University, Sankt-Peterburg, St.-Petersburg, Russia

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Publications (42)114.29 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: The rhodium(III) cationic methyl complexes, cis-[Rh(Acac)(PPh3)(2)(CH3)(DMF)][BPh4] (1) and cis[Rh(BA)(PPh3)(2)(CH3)(DMF)][BPh4] (2) are formed upon reactions of cis-[Rh(beta-diket)(PPh3)(2)(CH3)(MeCN)][BPh4] (beta-diket = acetylacetonate, Acac, or benzoylacetonate, BA) with excess of dimethylformamide (DMF) in CH2Cl2 solution at ambient temperature. Complexes 1 and 2 were characterized by elemental analysis, P-31{H-1} and H-1 NMR spectra, and single crystal X-ray crystallography. The cations of 1 and 2 have slightly distorted octahedral geometry. The "equatorial" plane contains the beta-diketonate and two PPh3 ligands; methyl and DMF ligands occupy the axial positions. Peculiar features of complexes 1 and 2 in solid state are: (i) unusually long Rh-O(DMF) bond and (ii) non-symmetrical orientation of the formyl C-H bond in relation to two oxygen atoms of the beta-diketonate ligand. The signals from formyl protons in the H-1 NMR spectra of 1 and 2 are shifted significantly upfield relatively to free DMF. The hydrogen bonding between formyl proton and one of the beta-diketonate oxygen atoms is considered. In solutions, 1 and 2 show dynamic behavior at ambient temperature and keep their solid-state geometry at -70 degrees C.
    Journal of Organometallic Chemistry 12/2014; 774:1–5. DOI:10.1016/j.jorganchem.2014.09.035 · 2.30 Impact Factor
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    ABSTRACT: A new rhodium(I) dimethyl sulfoxide (DMSO) 8-oxyquinolinato (Oxq) complex, [ Rh(Oxq)(CO)(DMSO)] (I), has been prepared and characterized by IR, H-1 and C-13 NMR, and X-ray data. DMSO is S-coordinated in the trans-N position. The values of nu(CO), carbonyl delta S-13, as well as delta C-13 and delta H-1 of Oxq ligand for three L trans-N complexes, [RhOxq(CO)(L)] (L = NH3, DMSO, and CO), define the intermediate position of DMSO within the ligand L series ranged in their net donating potency. Observed spin-spin couplings of Oxq C-13 (C2, C3, C4a, C7, C8a) and H-1 (H2) nuclei to Rh-103 provide one more tool to study long-range interactions of Oxq rings with metallocenter and remote ligand L.
    Journal of Organometallic Chemistry 07/2014; 761:123–126. DOI:10.1016/j.jorganchem.2014.03.019 · 2.30 Impact Factor
  • E. Tupikina, S.N. Smirnov, P.M. Tolstoy
    Nuclear Magnetic Resonance in Condensed Matter (NMRCM 2013), Saint-Petersburg, Russia; 07/2013
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    ABSTRACT: The rhodium(III) cationic methyl acetamidine complex, trans-[Rh(Acac)(PPh3)2(CH3){NHC(NH2)CH3}][BPh4], (1) is formed upon the reaction of trans-[Rh(Acac)(PPh3)2(CH3)(CH3CN)][BPh4] with ammonia gas in CH2Cl2 solution at temperatures between −15 °C and −20 °C. Complex 1 was characterized by elemental analysis, 31P{1H} and 1H NMR spectra, and single crystal X-ray diffraction study. The cation of 1 has a slightly distorted octahedral structure. The equatorial plane contains the acetylacetonate, methyl, and acetamidine ligands; two PPh3 ligands occupy the axial positions . The acetamidine ligand adopts the Z-configuration stabilized by hydrogen bonding with the oxygen atom of the acetylacetonate ligand, HN–H⋯O (1.90 Å). Complex 1 reacts with ammonia gas at temperatures between 0 °C and 20 °C to form cationic monophosphine complex [Rh(Acac)(PPh3)(CH3){NHC(NH2)CH3}(NH3)][BPh4] (2). Complex 2 was characterized by 31P{1H} and 1H NMR spectra without isolation.
    Journal of Organometallic Chemistry 07/2013; 735:47–51. DOI:10.1016/j.jorganchem.2013.03.015 · 2.30 Impact Factor
  • Central European School on Physical organic Chemistry, Przesieka, Poland; 05/2013
  • Russian Journal of General Chemistry 03/2013; 83(3). DOI:10.1134/S1070363213030274 · 0.42 Impact Factor
  • VII Symposium "Nuclear Magnetic Resonance in Chemistry, Physics and Biological Sciences, Warsaw, Poland; 09/2012
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    ABSTRACT: A comparison of 13C NMR parameters shows a drastic increase of ipso carbon to phosphorus coupling constant, 'J(CP), on passing from triphenylphosphine to its oxide. As may be supposed, this increase is mainly caused by binding phosphorus atom with a strong electron acceptor partner, oxygen atom. If so, one would expect that the 'J(CP) values for PPh, ligand coordinated to the electron acceptor transition metal center, LM<—PPh3 , would lie within the interval limited by these two end-points. Experimental data and results of the DFT study provide support for this hypothesis by the example of a family of closely related rhodium carbonyl phosphine complexes containing beta-diketonate and beta-ketoiminate ligands. When complexes of the family are arranged in ascending order of v(CO) carbonyl stretching frequency i. e. in ascending order of net electron acceptor ability of the rhodium center, the 'J(CP) values increase in the same order. The data suggest that the ipso carbon coupling constant, 'J(CP), in the 13C NMRspectrum of PPh3 ligand may serve, along with commonly applied carbonyl group stretching frequency, as one more yardstick for the net electron acceptor ability of metal centers over a wide range of LM<— PPh3 complexes.
    ICCC 40, Valencia, Sp[ain; 09/2012
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    ABSTRACT: A comparison of 13C NMR parameters shows a drastic increase of ipso carbon to phosphorus coupling constant, 'J(CP), on passing from triphenylphosphine to its oxide. As may be supposed, this increase is mainly caused by binding phosphorus atom with a strong electron acceptor partner, oxygen atom. If so, one would expect that the 'J(CP) values for PPh, ligand coordinated to the electron acceptor transition metal center, LM<—PPh3 , would lie within the interval limited by these two end-points. Experimental data and results of the DFT study provide support for this hypothesis by the example of a family of closely related rhodium carbonyl phosphine complexes containing beta-diketonate and beta-ketoiminate ligands. When complexes of the family are arranged in ascending order of v(CO) carbonyl stretching frequency i. e. in ascending order of net electron acceptor ability of the rhodium center, the 'J(CP) values increase in the same order.
    ICCC 40, Valencia, Spain; 09/2012
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    ABSTRACT: Ten formally symmetric anionic OHO hydrogen bonded complexes, modeling Asp/Glu amino acid side chain interactions in nonaqueous environment (CDF(3)/CDF(2)Cl solution, 200-110 K) have been studied by (1)H, (2)H, and (13)C NMR spectroscopy, i.e. intermolecularly H-bonded homoconjugated anions of acetic, chloroacetic, dichloroacetic, trifluoroacetic, trimethylacetic, and isobutyric acids, and intramolecularly H-bonded hydrogen succinate, hydrogen rac-dimethylsuccinate, hydrogen maleate, and hydrogen phthalate. In particular, primary H/D isotope effects on the hydrogen bond proton signals as well as secondary H/D isotope effects on the (13)C signals of the carboxylic groups are reported and analyzed. We demonstrate that in most of the studied systems there is a degenerate proton tautomerism between O-H···O(-) and O(-)···H-O structures which is fast in the NMR time scale. The stronger is the proton donating ability of the acid, the shorter and more symmetric are the H-bonds in each tautomer of the homoconjugate. For the maleate and phthalate anions exhibiting intramolecular hydrogen bonds, evidence for symmetric single well potentials is obtained. We propose a correlation between H/D isotope effects on carboxylic carbon chemical shifts and the proton transfer coordinate, q(1) = (1)/(2)(r(OH) - r(HO)), which allows us to estimate the desired OHO hydrogen bond geometries from the observed (13)C NMR parameters, taking into account the degenerate proton tautomerism.
    The Journal of Physical Chemistry A 06/2012; 116(46). DOI:10.1021/jp304943h · 2.78 Impact Factor
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    ABSTRACT: The oxidative addition of CH3I to planar rhodium(I) complex [Rh(TFA)(PPh3)2] in acetonitrile (TFA is trifluoroacetylacetonate) leads to the formation of cationic, cis-[Rh(TFA)(PPh3)2(CH3)(CH3CN)][BPh4] (1), or neutral, cis-[Rh(TFA)(PPh3)2(CH3)(I)] (4), rhodium(III) methyl complexes depending on the reaction conditions. 1 reacts readily with NH3 and pyridine to form cationic complexes, cis-[Rh(TFA)(PPh3)2(CH3)(NH3)][BPh4] (2) and cis-[Rh(TFA)(PPh3)2(CH3)(Py)][BPh4] (3), respectively. Acetylacetonate methyl complex of rhodium(III), cis-[Rh(Acac)(PPh3)2(CH3)(I)] (5), was obtained by the action of NaI on cis-[Rh(Acac)(PPh3)2(CH3)(CH3CN)][BPh4] in acetone at −15 °C. Complexes 1–5 were characterized by elemental analysis, 31P{1H}, 1H and 19F NMR. For complexes 2, 3, 4 conductivity data in acetone solutions are reported. The crystal structures of 2 and 3 were determined. NMR parameters of 1–5 and related complexes are discussed from the viewpoint of their isomerism.
    Journal of Organometallic Chemistry 10/2011; 696(20):3214–3222. DOI:10.1016/j.jorganchem.2011.06.035 · 2.30 Impact Factor
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    ABSTRACT: We have followed by NMR the zero-point energy changes of the hydrogen bond proton in 1:1 acid-base complexes AHB triple bond {A—H···B <-–> Aδ-···H···Bδ+ <-–> A-···H—B+} as a function of the proton position between A and B. For this purpose, the isotopic fractionation factors K between the acid-base complexes AHB + Ph3COD···B –><- ADB + Ph3COH···B, where AH represents a variety of acids and B represents pyridine-15N, were measured around 110 K, using a 2:1 mixture of liquefied CDClF2-CDF3 as solvent. As under these conditions the slow hydrogen bond exchange regime is reached, the values of K could be obtained directly by integration of appropriate proton NMR signals. Using the valence-bond order concept established previously by crystallography, the fractionation factors and corresponding zero-point energy changes (ΔZPE) are related in a quantitative way to the hydrogen bond geometries, the 1H chemical shift of the hydrogen bond proton, and the pyridine-15N chemical shift. The K values are related in a quasi-linear way to the chemical shifts of the hydrogen bond proton, where the slope depends on whether the proton is closer to oxygen or nitrogen. In the region of the strongly hydrogen-bonded quasi-symmetric complexes, which are characterized by a strong hydrogen bond contraction, the variation of K is very small in spite of substantial proton displacements.Key words: NMR, isotopic fractionation, hydrogen bonding, acid-base complexes, proton transfer, geometric isotope effects.
    Canadian Journal of Chemistry 02/2011; 77:943-949. · 1.01 Impact Factor
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    ABSTRACT: The (1)H and (13)C NMR spectra of 17 OHN hydrogen-bonded complexes formed by CH(3)(13)COOH(D) with 14 substituted pyridines, 2 amines, and N-methylimidazole have been measured in the temperature region between 110 and 150 K using CDF(3)/CDF(2)Cl mixture as solvent. The slow proton and hydrogen bond exchange regime was reached, and the H/D isotope effects on the (13)C chemical shifts of the carboxyl group were measured. In combination with the analysis of the corresponding (1)H chemical shifts, it was possible to distinguish between OHN hydrogen bonds exhibiting a single proton position and those exhibiting a fast proton tautomerism between molecular and zwitterionic forms. Using H-bond correlations, we relate the H/D isotope effects on the (13)C chemical shifts of the carboxyl group with the OHN hydrogen bond geometries.
    The Journal of Physical Chemistry A 10/2010; 114(40):10775-82. DOI:10.1021/jp1027146 · 2.78 Impact Factor
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    ABSTRACT: ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
    ChemInform 07/2010; 26(30). DOI:10.1002/chin.199530143
  • ChemInform 07/2010; 24(29):no-no. DOI:10.1002/chin.199329163
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    ABSTRACT: (1)H, (2)H, (19)F and (15)N NMR spectra of a strongly hydrogen-bonded anionic cluster, CNHF(-), as an ion pair with a tetrabutylammonium cation dissolved in CDF(3)-CDF(2)Cl mixture were recorded in the slow exchange regime at temperatures down to 110 K. The fine structure due to spin-spin coupling of all nuclei involved in the hydrogen bridge was resolved. H/D isotope effects on the chemical shifts were measured. The results were compared with those obtained earlier for a similar anion, FHF(-), and interpreted via ab initio calculations of magnetic shielding as functions of internal vibrational coordinates, namely an anti-symmetric proton stretching and a doubly-degenerate bending. The values of primary and secondary isotope effects on NMR chemical shifts were estimated using a power expansion of the shielding surface as a function of vibrational coordinates. A positive primary isotope effect was explained as a result of the decrease of the hydron stretching amplitude upon deuteration. We show that the proton shielding surface has a minimum close to the equilibrium geometry of the CNHF(-) anion, leading to the positive primary H/D isotope effect in a rather asymmetric hydrogen bond. We conclude that caution should be used when making geometric estimations on the basis of NMR data, since the shapes of the shielding functions of the internal vibrational coordinates can be rather exclusive for each complex.
    Physical Chemistry Chemical Physics 08/2009; 11(25):5154-9. DOI:10.1039/b900152b · 4.20 Impact Factor
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    ABSTRACT: Trans-[RuPy4(CN)2 cleaves chloro-rhodium bridges in rhodium(I) binuclear complexes, [Rh(CO)2Cl]2, [Rh(Cod)Cl]2, and [(Cod)RhCl2Rh(CO)2] yielding heterometallic triad complexes, [(CO)2ClRh(NC)RuPy4(CN)RhCl(CO)2] (I), [(Cod)ClRh(NC)RuPy4(CN)RhCl(Cod)] (II), and [(Cod)ClRh(NC)RuPy4(CN)RhCl(CO)2] (III), respectively. In solutions, III coexists with equilibrium amounts of I and II in the near-binomial proportions. Under action of [Rh(CO)2Cl]2, II transforms into I with parallel formation of [Rh(Cod)Cl]2. Ligand effect transmission along the L-Rh-NC-Ru-CN-Rh-L′ chain is studied by 1H and 13C NMR. Chemical shifts δ1H and δ13C of Ru-bound Py ligands are sensitive to the nature of Rh-bound ligands. Values of δ1H and δ13C of Cod and 13C of CO ligands are sensitive to the ligands at the remote end of the L-Rh-NC-Ru-CN-Rh-L′ chain. Reaction of trans-[RuPy4(CN)2] with Rh2(OAc)4 yields an apparently linear polymer [-Rh(OAc)4Rh-NCRuPy4CN-]. Upon action of [Rh(CO)2Cl]2, the polymer decomposes yielding I and Rh2(OAc)4. X-ray structure data for I are given.
    Journal of Organometallic Chemistry 08/2009; 694(18):2917-2922. DOI:10.1016/j.jorganchem.2009.04.028 · 2.30 Impact Factor
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    ABSTRACT: Low-temperature (193 K) (1)H, (13)C and (13)N NMR spectra of blue- and red-shifting H-bonded complexes formed by fluoroform with various proton acceptors were measured. Experimental NMR parameters were Plotted versus the ab initio calculated H-bond strength (MP2/6-31+G(d, p) interaction energy varies from similar to 5 LIP to 25 kJ . mol(-1) in (lie series). We show that experimental (1)H and (15)N shieldings its well its the H/D isotope effect on (13)C shielding change monotonously with the calculated H-bond strengthening. The (13)C chemical shift and the CH scalar coupling change non-monotonously and the extremum points are situated approximately in the region of transformation from blue to red-shifting H-bonds. The most informative NMR feature is the H/D isotope effect on (15)N shielding which changes its sign upon transformation from blue- to red-shifting H-bonds. To rationalize these observations, ab initio calculations of (13)C and (15)N shielding as functions of C...H and C...N distances were performed for complexes of CHF(3) with acetonitrile (blue-shifting) and pyridine (red-shifting). The coupling Of the vibrations of the covalent Mid hydrogen bonds has been accounted for by direct computation of the distance C...N = integral(C...H) dependence. We demonstrate that the unusual sign of the H/D isotope effect on 15N chemical shift across it blue-shifting H-bond can be explained as a result of the inversion of the dynamic coupling of two vibrations.
    Zeitschrift für Physikalische Chemie 08/2008; 222(8-9):1225-1245. DOI:10.1524/zpch.2008.5385 · 1.18 Impact Factor
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    ABSTRACT: Selective oxidation of one (trans to N) carbonyl group in [Rh(8-Oxiquinolinato)(CO)2] with stoichiometric amount of Me3NO in MeCN produces a solution containing [Rh(Oxq)(CO)(Me3N)] and [Rh(Oxq)(CO)(MeCN)]. The ammonia complex, [Rh(Oxq)(CO)(NH3)], has been prepared by action of NH3 gas on this solution and characterized by IR, 1H and 13C NMR, and X-ray data. Spectral parameters, ν(CO), δ13C, and 1J(CRh), were measured in situ for a series of complexes [Rh(Oxq)(CO)(L)] (L=NAlk3, Py, PBu3, PPh3, P(OPh)3, C8H14) formed upon action of L on [Rh(Oxq)(CO)(NH3)] in THF. A new ν(CO) and δ13C based scale of σ-donor/π-acceptor properties of ligands L is proposed including NH3 and CO as the natural endpoints.
    Journal of Organometallic Chemistry 12/2007; 692(26):5788-5794. DOI:10.1016/j.jorganchem.2007.09.022 · 2.30 Impact Factor
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    ABSTRACT: As a model system for the internal and external aldimines of the coenzyme pyridoxal phosphate (PLP) in PLP dependent enzymes we have studied the 1H and 15N NMR spectra of the 15N labeled Schiff base 3-carboxy-5-methyl-salicylidenaniline (1) dissolved in CD2Cl2. 1 contains a charge relay system with two strongly coupled intramolecular hydrogen bonds of the OHOHN type. One-bond 15N1H scalar spin–spin coupling constants and chemical shifts of partially deuterated 1 were measured in the temperature range between 243 and 183 K and analyzed assuming an exchange between three tautomeric states exhibiting well defined hydrogen bond geometries. The analysis shows that the dominant structure 1b corresponds to the zwitterion OH⋯O−⋯HN+, where deuteration of one bond leads to a shortening of the other. This anti-cooperative effect is revealed by the vicinal isotope effects on the proton chemical shifts. By contrast, forms 1a and 1c are characterized by the structures OH⋯OH⋯N and O−⋯HO⋯HN+, correspondingly, whose hydrogen bonds exhibit a cooperative coupling. We predict that 1a will dominate at high temperatures and low dielectric constants, whereas 1c will dominate at low temperatures and large dielectric constants. The comparison with model systems which do not contain the additional COOH-group indicates that the latter is responsible for the dominance of the zwitterionic structure of the OHN hydrogen bond. The implications of these findings for the function of the coenzyme pyridoxal phosphate in its natural environment are discussed.
    Journal of Molecular Structure 11/2007; DOI:10.1016/j.molstruc.2007.04.015 · 1.60 Impact Factor

Publication Stats

601 Citations
114.29 Total Impact Points

Institutions

  • 1996–2014
    • Saint Petersburg State University
      • • Department of Organic Chemistry
      • • Institute of Radiophysics
      Sankt-Peterburg, St.-Petersburg, Russia
  • 1996–2010
    • Freie Universität Berlin
      • Institute of Chemistry and Biochemistry
      Berlín, Berlin, Germany
  • 1999
    • University of Kansas
      • Department of Chemistry
      Lawrence, Kansas, United States