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    Research details

    The studies reported here were carried out by me and my colleagues at Russian State Medical University (research group of Prof. Yu. I. Baukov), University of Oxford (research group of Prof. P. Mountford), University of Kentucky (research group of Prof. F. Ladipo), University of Dortmund (research group of Prof. K. Jurkschat), and The Open University (research group of Prof. A. Bassindale). In some cases my work was a part of larger projects, so please follow the links on this page or consult my publications for further details.

    My research work at Russian State Medical University have been focused primarily on synthesis and reactivity of lactamo- and amidomethyl derivatives of penta- and hexacoordinated Si, Ge and Sn. Organic complexes of Group 14 metals are particularly interesting due to their biological activity, stereochemical behaviour and relative flexibility of structural parameters.

    Complexes of pentacoordinated Si, Ge and Sn

    Reactions of polyfunctional germanes and stannanes with N-TMS amides and lactams led to a series of new compounds of pentacoordinated Ge [1, 2] and the first examples of their Sn analogues [3].

    Structures of Ge(V) and Sn(V) complexes

    An effective one-pot synthesis was developed for larger-scale preparations:

    One-pot synthesis of Ge(V) complexes

    According to X-ray studies, both Ge and Sn atoms have distorted TBP environments with axial O and Hal substituents. Replacement of Cl with Br enhances the O–Ge coordination while introduction of Ph group into lactam ring has the opposite effect.

    X-ray structure of a Ge(V) complex

    Reactions of pentacoordinated Si [4] and Ge [5] chlorides with Grignard reagents lead to N-(trialkylgermyl)methyl derivatives with apparently no O–Ge coordination:

    Reaction with Grignard reagent

    Chromatographic studies show that relative reactivities of pentacoordinated Si and Ge analogues in concurrent reactions with a Grignard reagent are very similar to each other but significantly higher than the reactivity of tetracoordinated Me3MCl (M = Si, Ge) model compounds [5].

    Reaction of N-TMS-methylacetamide with (ClCH2)2SiCl2 in presence of moisture yields a complex containing silicenium dication and unusual hydroxonium trichloride counter-ion [6]:

    Synthesis of dicationic Si(V) complex

    The environments of both Si atoms are nearly ideal TBP with axial O–Si–O fragments. The anion is held together by three strong H-bonds with O–Cl distances from 2.83 to 2.88Å.

    X-ray structure of dicationic Si(V) complex

    Multinuclear NMR studies indicate the existence of two diastereomers that retain their configurations in solution.

    Complexes of hexacoordinated Ge

    Reactions of (ClCH2)2GeX2 with N-TMS amides and lactams led to a series of hexacoordinated Ge complexes [712]:

    Synthesis of Ge(VI) dichlorides

    One or both halogen atoms in these compounds may be substituted with a wide range of ligands. The exact type of the product depends only on the nature of nucleophile regardless of the reagents ratio [9]:

    Nucleophilic substitution reactions at Ge(VI)

    Formation of iodides is usually accompanied with oxidation and hydrolysis which lead to of tri- and polyiodides. In one case a digermoxane complex [(L(5)2Ge)2O](I3)2 was isolated on a preparative scale. The structure of the dication is similar to that of previously described silicon derivative.

    According to X-ray data, the Ge atoms in L2GeY2 complexes have distorted octahedral environments with two halogen substituents in cis-positions.

    X-ray structure of a cis-L2GeX2 complex

    Formation of monosubstituted L2GeX(Z) derivatives always leads to trans-configuration of monodentate ligands. The central atoms in the latter complexes have strongly distorted TBP environments with additional Ge···Z interaction.

    X-ray structure of a trans-L2GeX(Z) complex

    X-ray structures of stable Ge complexes were used by us for modelling the SN-Ge reaction pathway [13]. The correlations between O–Ge bond length and ΔΩ = Ω0–Ω (where Ω0 and Ω are, respectively, ideal and actual spatial angles enclosing the "leaving" substituent) values demonstrate a relative independence of both hypervalent fragments of the central atom as well as similar sterical behaviour of penta- and hexacoordinated germanium.

    Spatial angle - Bond length plot

    NMR and IR data indicate the presence of strong O–Ge coordination in solutions of all studied complexes. Electroconductivity of dihalogenides L2GeX2 in CH2Cl2 solutions is relatively low but increases by an order on replacement of one halogen atom with a good leaving group.

    According to NMR data, both cis- and trans- complexes demonstrate some degree of stereochemical non-rigidity. However, the corresponding barriers are significantly different. This fact, along with IR and electroconductivity data, provides sufficient information not only to determine the structures of studied compounds but also to estimate the strength of coordination and in certain cases to suggest possible mechanisms of stereodynamic processes in their molecules [10, 11].

    Existence of stable complexes with hexacoordinated Ge atom indicates the possibility of associative mechanism for SN reactions at pentacoordinated Ge atom. At the same time higher electroconductivity and stereochemical behaviour of trans-L2GeX(Z) derivatives suggest that dissociative mechanism with the formation of germacenium intermediates [L2GeX]+ may be the main route of substitution reactions at hexacoordinated germanium.

    Complexes of hexacoordinated Sn

    In contrast to the Ge analogues, the reaction of N-TMS lactams with (ClCH2)2SnCl2 requires very high temperatures and leads to significant decomposition of the products [14]:

    Synthesis of Sn(VI) dichlorides

    We discovered that these compounds may be prepared with high yields by direct synthesis from metal tin and N-halogenomethylamides or -lactams [11, 15, 16]:

    Direct synthesis of L2SnX2

    Dibromides and diiodides were also prepared by exchange reactions with corresponding lithium salts [16]:

    Nucleophilic substitution reactions at Sn(VI)

    Structures and stereodynamic behaviour of these complexes are similar to those of the corresponding Ge analogues. X-ray and NMR studies indicate that hexacoordination and cis-configuration of monodentate ligands retain both in solid state and solutions [11, 14, 16].

    X-ray structure of an L2SnX2 complex

    In contrast to germanium, reactions of dichlorides L2SnCl2 with LiI lead to formation of stable diiodides L2SnI2 as a result of lower sterical hindrance in the Sn coordination environment.

    Reaction of L2SnCl2 with AgBF4 in the presence of moisture produced a dimeric cation-anionic complex [17]:

    X-ray structure of dicationic Sn(VI) complex

    The optimal conditions for this type of reactions are still to be found, but it should be noted that none of the "butterfly-type" complexes of Si, Ge or Sn could be isolated until the reaction mixture was exposed to traces of moisture and oxygen.

    In 1999 Dr. Vad. V. Negrebetsky and I were awarded the State Prize of Russian Federation for our studies in "Dynamic Stereochemistry of Penta- and Hexacoordinated Compounds of Silicon, Germanium and Tin". The large part of this investigation belongs to our research group at the Chemistry Department of Russian State Medical University (supervisor — Prof. Yu. I. Baukov). Without their efforts none of the results reported here could ever be achieved.

    Triazacyclononane complexes of Ga, In, Tl and earlier transition metals

    In 1999–2000 I worked as a post-doctoral fellow at the University of Oxford in the research group of Prof. P. Mountford. My project included synthesis, NMR studies and initial testing of catalytic activity of macrocyclic complexes of Groups 13 and 3–6 metals.

    Complexes of both main group and early transition metals with mono-pendant arm triazacyclononane derivatives were prepared from the corresponding metal trichlorides or their THF complexes and potassium salts of the ligand [18, 19]:

    Structures of triazacyclononane complexes

    In the case of Tl(I), an alternative synthetic route (reaction of thallium ethoxide with a free ligand) was explored. Reactions with free ligands were also used for the preparation of organometallic derivatives of indium from trialkylindium. The organoscandium and -yttrium compounds were synthesised from the corresponding dichlorides and organolithium reagents.

    According to crystallographic and NMR data, central atoms in most of the complexes have distorted octahedral environments both in the solid state and in solutions [18].

    X-ray structure of an In(III) complex

    Thallium(I) complexes have distorted pseudo-TBP structures with the lone electron pair occupying one of the equatorial positions [19].

    X-ray structure of a Tl(I) complex

    Dichlorocomplexes in solutions are rigid with the exception of Ga derivatives that undergo dynamic processes at RT. However, NMR studies indicate that at lower temperatures the structures of gallium complexes are essentially the same as those of other compounds. Thallium(III) derivatives are dimeric in solutions although their structures are still to be found. Dynamic processes in solutions of Tl(I) compounds were also observed but the structures could not be frozen even at –90°C. Preliminary polymerisation tests of some compounds have been obtained and further work is in progress at the Prof. Mountford group.

    Calixarene-supported complexes of Ti and Zr

    In 2000–2001 I worked for several months as a post-doctoral scholar at University of Kentucky (Lexington, KY, USA) in the research group of Prof. F. Ladipo. My work was focused on synthesis and NMR studies of calix[4]arene derivatives of Ti and Zr with potential catalytic activity in polymerisation reactions.

    General structure of calixarene complexes

    Some of the Ti-calixarene complexes prepared by Prof. Ladipo research group demonstrated highly regioselective catalytic activity in cycloaddition reactions of terminal alkynes. In the course of my work new ligands and complexes were prepared and studied by NMR and X-ray methods [20]. At present the work in this area is in progress at the Prof. Ladipo group.

    Neutral and cation-anionic organotin compounds (University of Dortmund)

    The review of my post-doctoral research at the University of Dortmund (Dortmund, Germany, 2003) will be added in a short time.

    (O,O)-chelate complexes of hypercoordinate silicon and germanium (The Open University)

    The review of my post-doctoral research at the Open University (Milton Keynes, UK, 2007) will be added in a short time.

    I would like to express my gratitude to all the people I had an opportunity to work with. Special thanks to my teachers and advisors, Prof. Yu. I. Baukov, Prof. P. Mountford, Prof. F. Ladipo, Prof. K. Jurkschat, Prof. P. Taylor, and Prof. A. Bassindale. Their advice, concern, and encouragement have been essential for any results and achievements reported here.

    [01]   Bylikin S. Yu., Pogozhikh S. A., Khrustalev V. N., Negrebetsky Vad. V., Shipov A. G., Ovchinnikov Y. E., Baukov Yu. I. Synthesis, crystal and molecular structures, and stereochemical non-rigidity of N-(chlorodimethylgermylmethyl)- and N-(bromodimethylgermylmethyl)-N-[(S)-1-phenylethyl]acetamides and N-(chlorodimethylgermylmethyl)-4-phenyl-2-pyrrolidone. // Russ. Chem. Bull. 2000. V. 49. No. 1. P. 140–147.
    [02]   Bylikin S. Yu., Kramarova E. P., Shipov A. G., Negrebetsky Vad. V., Baukov Yu. I. Synthesis and thermal stability of N-[(dimethylchlorogermyl)methyl]-N-methyl-O-trimethylsilylsalicylamide. // Zhurnal Obshchei Khimii. 2001. V. 71. No. 8. P. 1401–1402 (in Russian).
    [03]   Bylikin S. Yu., Shipov A. G., Negrebetsky Vad. V., Baukov Yu. I., Ovchinnikov Yu. E., Pogozhikh S. A., Pestunovich S. V., Belousova L. I., Belogolova E. F., Sidorkin V. F., Voronkov M. G., Pestunovich V. A., Kalikhman I., Kost D. Reaction of N-trimethylsilyl derivatives of amides and lactams with chloro(chloromethyl)dimethylstannane. Crystal and molecular structure of 1-(chlorodimethylstannylmethyl)-2-piperidone. // J. Organometal. Chem. 2006. Vol. 691. No. 4. P. 779–786.
    [04]   Shipov A. G., Kramarova E. P., Artamkina O. B., Baukov Yu. I. Reaction of N-(dimethylchlorosilylmethyl)lactams with Grignard reagents. Enhanced reactivity of the silylchlorides with pentacoordinated silicon in comparison with trimethylchlorosilane. // Metalloorg. Chem. 1991. V. 4. No. 5. P. 1101–1106 (in Russian).
    [05]   Bylikin S. Yu., Shipov  A. G., Kramarova  E. P., Artamkina  O. B., Negrebetsky  Vad. V., Baukov  Yu. I. Reactivity of N-(dimethylchlorgermyl)methyl and N-(dimethylchlorosilylmethyl) lactams and amides towards Grignard reagents. // Russ. J. Gen. Chem. 2004. Vol. 74. No. 9. P. 1356–1359.
    [06]   Ovchinnikov Yu. E., Pogozhikh S. A., Razumovskaya I. V., Shipov A. G., Kramarova E. P., Bylikin S. Yu., Negrebetsky Vad. V., Baukov Yu. I. Synthesis, crystal and molecular structure of cation-anionic complexes of five-coordinated silicon containing disiloxane dications with lactamomethyl and N-methylacetamidomethyl C,O-chelating ligands. // Russian Chemical Bulletin. 1998.Vol. 47. No. 5. P. 967–978.
    [07]   Baukov Yu. I., Shipov A. G., Smirnova L. S., Kramarova E. P., Bylikin S. Yu., Ovchinnikov Yu. E., Struchkov Yu. T. Interaction of the (O–Ge)-chelate bis-(lactamo-N-methyl)-cis-dichlorogermanes with trimethylsilyl triflate. Synthesis of bis(lactamo-N-methyl)-trans-(trifluoromethylsulfonyloxy)chlorogermanes. // J. Organomet. Chem. 1993. V. 461. No. 1–2. P. 39–42.
    [08]   Ovchinnikov Yu. E., Struchkov Yu. T., Baukov Yu. I., Shipov A. G., Kramarova E. P., Bylikin S. Yu. Structures of organic derivatives of hexacoordinated germanium. (O–Ge)-chelated bis(2-oxo-1-hexahydroazepinylmethyl)chlorogermane iodide and bis-(2-oxo-1-hexahydroazepinylmethyl)chlorogermane triiodide. // Izv. Akad. Nauk, Ser. Khim. 1994. No. 8. P. 1421–1426 (in Russian).
    [09]   Ovchinnikov Yu. E., Struchkov Yu. T., Baukov Yu. I., Shipov A. G., Bylikin S. Yu. Structures of organic derivatives of hexacoordinated germanium. (O–Ge)-chelated bis(2-oxo-1-hexahydroazepinylmethyl)difluorogermane and bis-(2-oxo-1-hexahydroazepinylmethyl)fluorogermane tetrafluoroborate. // Russian Chemical Bulletin. 1994. V. 43. No. 8. P. 1351–1355.
    [10]   Bylikin S. Yu., Shipov A. G., Kramarova E. P., Negrebetsky Vad. V., Smirnova L. S., Pogozhikh C. A., Ovchinnikov Yu. E., Baukov Yu. I. Peculiarities of nucleophilic substitution at hexacoordinate germanium atom in (O–Ge)-bischelate bis(lactamomethyl)dichlorogermanes. // Zhurnal Obshchey Khimii. 1997. V. 67. No. 11. P. 1850–1865 (in Russian).
    [11]   Pogozhikh S. A., Ovchinnikov Yu. E., Bylikin S. Yu., Negrebetsky Vad. V., Shipov A. G., Baukov Yu. I. Synthesis, crystal and molecular structure and stereochemical non-rigidity of bis[(N-methylacetamido)methyl]dichlorogermane and -dichlorostannane. // Russ. J. Gen. Chem. 2000. V. 70. No. 4. P. 533–538.
    [12]   Ovchinnikov Yu. E., Pogozhikh S. A., Khrustalev V. N., Bylikin S. Yu., Negrebetsky Vad. V., Shipov A. G., Baukov Yu. I. Crystal and molecular structures of six-coordinate germanium difluorides and dibromides containing lactamomethyl C,O-chelating ligands. // Russ. Chem. Bull. 2000. V. 49. No. 10. P. 1775–1781.
    [13]   Ovchinnikov Yu. E., Struchkov Yu. T., Shipov A. G., Smirnova L. S., Baukov Yu. I., Bylikin S. Yu. Modelling of hexacoordinated transition states of germanium based on the crystal structures of germanium-substituted bis(lactamo-N-methyl)germanes L2GeX2 and L2GeXY (X, Y = Hal, OTf, BF4, I3). // Mendeleev Commun. 1994. No. 5. P. 178–180.
    [14]   Bylikin S. Yu., Shipov A. G., Negrebetsky Vad. V., Smirnova L. S., Baukov Yu. I., Ovchinnikov Yu. E., Struchkov Yu. T. Synthesis, crystal structure and stereochemical non-rigidity of (O–Sn)-bischelated bis(lactamomethyl)dichlorostannanes. // Russian Chemical Bulletin. 1996. V. 45. No. 11. P. 2627–2638.
    [15]   Shipov A. G., Bylikin S. Yu., Negrebetsky Vad. V., Baukov Yu. I. Direct synthesis of bis(O–Sn)-chelate bis(lactamo-N-methyl)dichlorostannanes. // Zhurnal Obshchey Khimii. 1995. V. 65. No. 12. P. 2066–2067 (in Russian).
    [16]   Ovchinnikov Yu. E., Pogozhikh S. A., Razumovskaya I. V., Bylikin S. Yu., Shipov A. G., Smirnova L. S., Negrebetsky Vad. V., Baukov Yu. I. Synthesis, crystal and molecular structure of dibromides and diiodides of hexacoordinated tin containing lactamomethyl C,O-chelating ligands. // Russian Chemical Bulletin. 1999. V. 48. No. 10. 1964–1974.
    [17]   Bylikin S. Yu., Pogozhikh S. A., Shipov A. G., Negrebetskii Vad. V., Ovchinnikov Yu. E., Baukov Yu. I. Unexpected formation of a dimeric cation-anionic complex of hypercoordinated tin in the reaction of bis[(2-oxopyrrolidino)methyl]tin dichloride with AgBF4. // Russ. Chem. Bull. 2000. V. 49. No. 4. P. 755–757.
    [18]   Robson D. A., Bylikin S. Y., Cantuel M., Male N. A. H., Rees L. H., Mountford P., Schroeder M. Neutral and cationic organometallic aluminium and indium complexes of mono-pendant arm triazacyclononane ligands. // Dalton Trans. 2001. No. 2. P. 157–169.
    [19]   Bylikin S. Y., Robson D. A., Male N. A. H., Rees L. H., Mountford P., Schroeder M. New main group and early transition metal complexes of mono-pendant arm triazacyclononane ligands. // Dalton Trans. 2001. No. 2. P. 170–180.
    [20]   Ladipo F. T., Sarveswaran V., Kingston J. V., Huyck R. A., Bylikin S. Yu., Carr S. D., Watts R., Parkin S. Synthesis, characterization, and alkyne cyclotrimerization chemistry of titanium complexes supported by calixarene-derived bis(aryloxide) ligation. // J. Organomet. Chem. 2004. Vol. 689. No. 3. P. 502–514.