Ilya E. Nifant'ev

Zr and Hf metallocenes. Study of the structure of a novel mononuclear zirconium trivalent organometallic

Cp2∗MCl2, M  Zr and Hf, were obtained by reaction of MCl4 with Cp∗Li, where Cp∗  1,3-di-tertbutylcyclopentadienyl. Reduction of Cp2∗MCl2 with metallic potassium in pentane gave Cp2∗MCl. The molecular and crystal structure of Cp2∗ZrCl was established from X-ray diffraction; monoclinic, space group P21/b, a  12.722, b  16.336, c  13.426 A, γ  70.68°, R  0.065; monomeric Cp2∗ZrCl molecules, the average ZrC bond length is 2.505 A, that of ZrCl is 2.423 A, and the Cp∗centroidZrCp∗centroid angle is 133.3°.

C2‐Symmetric Zirconocenes for High Molecular Weight Amorphous Poly(propylene)

Details of the preparation and polymerization behavior of two chiral zirconocene catalysts are presented. The results of experimental and molecular-mechanics evaluation of their stereoselectivity with respect to liquid-propene polymerization are compared with those of a related catalyst system. The elastic properties of the obtained amorphous poly(propylene) due to the presence of small γ-form crystallites, are compared with those of a high-molecular weight atactic poly(propylene) obtained in the presence of a C 2v catalyst.

ansa-Metallocene derivatives of TiIV and ZrIV with the shortest -C(CH3)2- bridge

Abstract Novel C(CH3)2 bridged molecules, (CH3)2C(C5H4)2M(CH3)2, M = Ti, Zr, were synthesized. The structures of both molecules were determined by X-ray diffraction analysis. For the Ti compound: crystals, monoctinic; space group, P21, / m, a = 7.196(4), b = 10.227(1), c = 8.941(3) A, γ = 89.95°. For Zr compound: crystals, monoclinic; space group P21 / m, a = 7.333(4), b = 10.429(3), c = 9.031(6) A, γ = 89.98°. Both molecules are characterized, as expected, by significant intramolecular tension resulting in obvious distortion of the sandwich moiety.

Binuclear and mononuclear di-η5-cyclopentadienylniobium chemistry: a new insight. Crystal and molecular structure of [Cp2NbH2]−[Na · benzo-15-crown-5]+

Abstract A mononuclear di-η 5 -cyclopentadienylniobium complex Cp 2 NbH 2 Na (I) has been found to be a by-product of the reaction of Cp 2 NbCl 2 with NaH, the principal products being (η 5 : η 1 -C 5 H 4 ) 2 Cp 2 Nb 2 H 2 ) 2 (II) in THF and (η 5 : η 5 -C 5 H 4 C 5 H 4 )Cp 2 -Nb 2 (η-H) 2 (III) in DME. Cp 2 NbH 2 Na wasalso obtained by reaction of Cp 2 NbH 3 or the mixture of Cp 2 NbBH 4 + Et 3 N with NaH. Crystal and molecular structure of [Cp 2 NbH 2 ] − [Na · NbH 2 − [Na · B15C5] + (Ia) (B15C5 = benzo-15-crown-5) was established by an X-ray diffraction study (4208 reflections, R = 0.022; monoclinic, at −120° C, a 17.345(3), b 11.742(3), c 22.965(5) A, β 98.52(1)°, Z = 8 space group C 2/ c ). The structural data indicate substantial ionic character of the (Cp 2 NgH 2 ) − … (Na · B15C5) + interaction in the solid.

Synthesis and chemical properties of μ-hydrido-μ-halogenodicyclopentadienylfulvalenediniobium

Bis-niobocene (η5 : η1-C5H4)2Nb2H2 when treated with organic halides, e.g. C4H9Cl, C6H5CH2Cl, CCl4, CHCl3, CH3I and C2H5Br gives quantitatively new fulvalene complexes (η5 : η5-C10H8)(C5H5)2Nb2(μ-Hal). The complex (η5 :η5)-C10H8)(C5H5)2Nb2(μ-H)(μ-Cl) readily exchanges its bridging chlorine atom for methoxy and ethoxy groups or a hydride ligand. Reaction with water gives a diamagnetic compound, for which the structure (η5 : η5-C10H8)(C5H5)2(Cl)2Nb2(μ-O) is proposed. A new method for the synthesis of bis-niobocene through interaction of (C5H5)2NbCl2 with NaH in THF was found. It is shown that in DME the same reaction between (C5H5)2NbCl2 and NaH gives an isomeric fulvalene complex (η5 : η5-C10H8)(C5H5)2Nb2(μ-H)2 instead.

The stoichiometry of protein phosphorylation in adipocyte lipid droplets: Analysis by N-terminal isotope tagging and enzymatic dephosphorylation

Most phosphoproteomic studies to date have been limited to the identification of phosphoproteins and their phosphorylation sites, and have not assessed the stoichiometry of protein phosphorylation, a critical parameter reflecting the dynamic equilibrium between phosphorylated and non‐phosphorylated pools of proteins. Here, we used a method for measuring phosphorylation stoichiometry through isotope tagging and enzymatic dephosphorylation of tryptic peptides. Using this method, protein digests are divided into two equal aliquots that are modified with either light or heavy isotope tags. One aliquot is dephosphorylated by alkaline phosphatase. Finally, the peptide mixtures are recombined and LC‐MS/MS analysis is performed. With this method, we studied adipocytes of mice stimulated with CL316,243, a β‐3 adrenergic agonist known to induce lipolysis and marked phosphorylation changes in proteins of the lipid droplet surface. In lipid droplet preparations, CL316,243 administration increased phosphorylation of proteins related to regulation of signaling, metabolism and intracellular trafficking in white adipose tissue, including hormone‐sensitive lipase which was 80% phosphorylated at the previously reported site, Ser‐559, and the lipid surface protein perilipin, which was phosphorylated by ∼60 and ∼40% at previously unreported sites, Ser‐410 and Ser‐460.

Synthesis of polyacrylonitrile copolymers as potential carbon fibre precursors in CO2

Binary and ternary acrylonitrile (AN) copolymers with methyl acrylate (MA) and either itaconic acid (IA, 1) or IA derivatives (monomethyl itaconate (2), monoethyl itaconate (3), IA monoamide (4), IA mono-n-octylamide (5)) were prepared in CO2. The obtained copolymers have good morphological and molecular weight characteristics. They demonstrate broad heat evolution during thermal cyclisation according to DSC measurements; therefore, they may be used to produce carbon fibres. The polymer yield per reaction volume is 2 to 3 times higher relative to that produced in solution (in DMSO or DMF) or an aqueous suspension.

A facile synthesis of 2-arylindenes by Pd-catalyzed direct arylation of indene with aryl iodides

Abstract A series of 2-arylindenes were prepared by the reaction of aryl iodides with indene in the presence of a catalytic amount of Pd(OAc)2.

METALLOCENEPHOSPHORAMIDES, 2.∗ AMIDES OF FERROCENEPHOSPHONOUS AND FERROCENEDIPHOSPHONOUS ACIDS

Abstract The first examples of phosphorylated metallocenes containing P(III)-N bond were prepared. Two synthetic routes were developed: treating iron(II)bromide with phosphorylated sodium cyclopentadienide and the reaction of mono- and dilithiated ferrocenes with chlorides of diamidophosphorous acids. Two heterocyclic amides were obtained via chlorides of ferrocenedisphosphonous acid.

Global analysis of protein phosphorylation networks in insulin signaling by sequential enrichment of phosphoproteins and phosphopeptides

Although the important role of protein phosphorylation in insulin signaling networks is well recognized, its analysis in vivo has not been pursued in a systematic fashion through proteome-wide studies. Here we undertake a global analysis of insulin-induced changes in the rat liver cytoplasmic and endosomal phosphoproteome by sequential enrichment of phosphoproteins and phosphopeptides. After subcellular fractionation proteins were denatured and loaded onto iminodiacetic acid-modified Sepharose with immobilized Al³⁺ ions (IMAC-Al resin). Retained phosphoproteins were eluted with 50 mM phosphate and proteolytically digested. The digest was then loaded onto an IMAC-Al resin and phosphopeptides were eluted with 50 mM phosphate, and resolved by 2-dimensional liquid chromatography, which combined offline weak anion exchange and online reverse phase separations. The peptides were identified by tandem mass spectrometry, which also detected the phosphorylation sites. Non-phosphorylated peptides found in the flow-through of the IMAC-Al columns were also analyzed providing complementary information for protein identification. In this study we enriched phosphopeptides to ~85% purity and identified 1456 phosphopeptides from 604 liver phosphoproteins. Eighty-nine phosphosites including 45 novel ones in 83 proteins involved in vesicular transport, metabolism, cell motility and structure, gene expression and various signaling pathways were changed in response to insulin treatment. Together these findings could provide potential new markers for evaluating insulin action and resistance in obesity and diabetes.