Stanislav Groysman
Wayne State University
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Featured researches published by Stanislav Groysman.
Biochemistry | 2009
Stanislav Groysman; R. H. Holm
Biomimetic inorganic chemistry has as its primary goal the synthesis of molecules that approach or achieve the structures, oxidation states, and electronic and reactivity features of native metal-containing sites of variant nuclearity. Comparison of properties of accurate analogues and these sites ideally provides insight into the influence of protein structure and environment on intrinsic properties as represented by the analogue. For polynuclear sites in particular, the goal provides a formidable challenge for, with the exception of iron-sulfur clusters, all such site structures have never been achieved and few have even been closely approximated by chemical synthesis. This account describes the current status of the synthetic analogue approach as applied to the mononuclear sites in certain molybdoenzymes and the polynuclear sites in hydrogenases, nitrogenase, and carbon monoxide dehydrogenases.
Inorganica Chimica Acta | 2003
Stanislav Groysman; Israel Goldberg; Moshe Kol; Elisheva Genizi; Zeev Goldschmidt
Abstract A new amine bis(phenolate) ligand bearing a THF donor on a sidearm and several dialkyl complexes of the group IV triad are introduced. The crystal structures of a zirconium dibenzyl complex and a titanium dibenzyl complex were solved, and revealed a strong binding of the oxygen donor of the THF group to the metal center. Upon activation with tris(pentafluorophenyl)borane the zirconium and the hafnium dibenzyl complexes lead to highly active 1-hexene polymerization catalysts. In comparison, titanium complexes (a dibenzyl complex and a dimethyl complex) lead to slower but living polymerization of 1-hexene at room temperature. Polymerization of neat 1-hexene under high dilution conditions was found to be living for an exceptionally long time of 6 days, leading to poly(1-hexene) of Mw=816 000 and PDI=1.09. A block copolymerization of 1-hexene and 1-octene at room temperature could be obtained using the titanium catalysts.
Inorganic Chemistry | 2009
Stanislav Groysman; R. H. Holm
A series of two-coordinate thiolate complexes [Cu(SAr*)L] was synthesized as possible reactants in forming analogues of the active site of Mo/Cu-containing carbon monoxide dehydrogenase. Complexes with L = PPh(3) (1), 2,6-lutidine (2), and the N-heterocyclic carbene Pr(i)(2)NHCMe(2) (3) have been prepared by the reaction of [CuCl(PPh(3))(3)] (1) or [CuBr(SMe(2))] (2, 3) with ligand L and the exceptionally sterically encumbered ligand Ar*S = 2,6-bis(2,4,6-triisopropylphenyl)benzenethiolate(1-). The reaction of [CuBr(SMe(2))] with the thiolate in the absence of added L afforded trinuclear [Cu(3)(SAr*)(2)Br] (7). The carbene complex (3) undergoes Cu-C bond insertion with sulfur to form the thiourea complex [Cu(SAr*)(Pr(i)(2)Me(2)ImS)] (4). The complexes [Cu(Ar*)L] with L = tetrahydrothiophene (5) and 2,6-lutidine (6) were obtained by reaction of Ar*Li(OEt(2)) with CuBr/L. These species did not undergo clean Cu-C bond insertion with sulfur transfer agents; the disulfide Ar*SSCH(2)Ph (9) was isolated from the reaction of 6 with (PhCH(2)S)(2)S. The structures of all complexes and 9 were determined. Whereas 5 and 6 are strictly two-coordinate with linear C-Cu-L angles, 1-4 are quasi-two-coordinate because of weak 3d-C(ppi) interactions with a phenyl group, leading to nonlinear structures (S-Cu-L = 135-164 degrees).
Journal of the American Chemical Society | 2008
Stanislav Groysman; Jun Jieh Wang; Ranitendranath Tagore; Sonny C. Lee; R. H. Holm
Two series of square pyramidal (SP) monodithiolene complexes, [M (VI)O 3- n S n (bdt)] (2-) and their silylated derivatives [M (VI)O 2- n S n (OSiR 3)(bdt)] (-) ( n = 0, M = Mo or W; n = 1, 2, M = W), synthesized in this and previous work, constitute the basic molecules in a biomimetic approach to structural analogues of the oxidized sites in the xanthine oxidoreductase enzyme family. Benzene-1,2-dithiolate (bdt) simulates native pyranopterindithiolene chelation in the basal plane, tungsten instead of the native metal molybdenum was employed in sulfido complexes to avoid autoreduction, and silylation models protonation. The complexes [MO 3(bdt)] (2-) and [MO 2(OSiR 3)(bdt)] (-) represent inactive sites, while [MO 2S(bdt)] (2-) and [MOS(OSiR 3)(bdt)] (-), with basal sulfido and silyloxo ligands, are the first analogues of the catalytic sites. Also prepared were [MOS 2(bdt)] (2-) and [MS 2(OSiR 3)(bdt)] (-), with basal sulfido and silyloxo ligands. Complexes are described by angular parameters which reveal occasional distortions from idealized SP toward a trigonal bipyramidal (TBP) structure arising from crystal packing forces in crystalline Et 4N (+) salts. Miminized energy structures from DFT calculations are uniformly SP and reproduce experimental structures. For example, the correct structure is predicted for [WO 2S(bdt)] (2-), whose basal and apical sulfido diastereomers are potentially interconvertible through a low-lying TBP transition state for pseudorotation. The lowest energy tautomer of the protonated form is calculated to be [WOS(OH)(bdt)] (-), with basal sulfido and hydroxo ligands. Computational and experimental structures indicate that protein sites adopt intrinsic coordination geometries rather than those dictated by protein structure and environment.
Journal of The Chemical Society-dalton Transactions | 2002
Stanislav Groysman; Sharon Segal; Marina Shamis; Israel Goldberg; Moshe Kol; Zeev Goldschmidt; Einat Hayut-Salant
A tetradentate trianionic amine triphenolate ligand leads to octahedral Ta(V) complexes of Cs-symmetry, in which the two labile positions that are in cis geometry exhibit a dramatic difference in reactivity, the position trans to a phenoxy group being the active one.
Inorganic Chemistry | 2013
Matthew B. Chambers; Stanislav Groysman; Dino Villagrán; Daniel G. Nocera
Mononuclear Fe(II) and Fe(III) complexes residing in a trigonal tris(ditox) (ditox = (t)Bu2(Me)CO(-)) ligand environment have been synthesized and characterized. The Fe(III) ditox complex does not react with oxidants such as PhIO, whereas NMe3O substitutes a coordinated tetrahydrofuran (THF) in the apical position without undergoing oxo transfer. In contrast, the Fe(II) ditox complex reacts rapidly with PhIO or Me3NO in THF or cyclohexadiene to furnish a highly reactive intermediate, which cleaves C-H bonds to afford the Fe(III)-hydroxide complex. When generated in 1,2-difluorobenze, this intermediate can be intercepted to oxidize phosphines to phosphine oxide. The fast rates at which these reactions occur is attributed to a particularly weak ligand field imparted by the tris(alkoxide) ancillary ligand environment.
Inorganic Chemistry | 2013
James A. Bellow; Philip D. Martin; Richard L. Lord; Stanislav Groysman
The iron(III) hexazene complex (RO)2Fe(μ-κ(2):κ(2)-AdN6Ad)Fe(OR)2 (3) was synthesized via reductive coupling of 1-azidoadamantane at the iron(II) bis(alkoxide) complex Fe(OR)2(THF)2 (2). The X-ray crystal structure depicts electron delocalization within the hexazene moiety. Density functional theory studies propose the formation of an iron azide dimer on the route to hexazene, in which each azide is monoreduced and the iron centers are oxidized to the 3+ oxidation state.
Israel Journal of Chemistry | 2002
Stanislav Groysman; Edit Y. Tshuva; Dvora Reshef; Shimrit Gendler; Israel Goldberg; Moshe Kol; Zeev Goldschmidt; Michael Shuster; Gershon Lidor
The polymerization of propylene employing the recently developed amine bis(phenolate) zirconium catalysts is reported for the first time. The polymerizations were conducted in liquid propylene employing two different experimental setups, and two different precatalysts, based on the same amine bis(phenolate) ligand having a dimethylamino donor on a sidearm. The first precatalyst studied was a dibenzyl zirconium complex, which was found to lead to high molecular weight atactic polypropylene. The effects of the cocatalyst, the ratio between the cocatalyst and the precatalyst, and the polymerization temperature on the nature of the resulting polymer and the activity of the catalyst were studied. Reducing the relative amount of the cocatalyst and lowering the polymerization temperature increased the molecular weight of the polymer, and a temperature of 50 °C led to the most active catalyst. A dichloro zirconium complex of the same ligand, expected to show a higher hydrolytic and thermal stability was developed, its X-ray structure was solved, and its activity in polymerization of propylene was studied and found to be similar to that of the dibenzyl precatalyst.
Journal of the American Chemical Society | 2016
James A. Bellow; Sebastian A. Stoian; Johan van Tol; Andrew Ozarowski; Richard L. Lord; Stanislav Groysman
The formally Co(IV) carbene Co(OR)2(═CPh2) is formed upon the reaction of diphenyldiazomethane with the cobalt bis(alkoxide) precursor Co(OR)2(THF)2. Structural, spectroscopic, and theoretical studies demonstrate that Co(OR)2(═CPh2) has significant high-valent Co(IV)═CPh2 character with non-negligible spin density on the carbene moiety.
Chemistry: A European Journal | 2013
James A. Bellow; Dong Fang; Natalija Kovacevic; Philip D. Martin; Jason Shearer; G. Andrés Cisneros; Stanislav Groysman
Caution! Chemists playing: Novel clusters of the form [M2Li2Cl2(OR)4] featuring rare seesaw geometry at the transition metal centers were synthesized for M=Cr-Co. The use of sterically hindering alkoxide ligands, as well as the inclusion of lithium ions in the structures enforces this highly unusual configuration.