Synthesis of new titanatranes containing organic substituents in the atrane fragment

Titanatrane CpTi(OCH(CH₃)CH₂)₃N (3) was prepared by the reaction of CpTiCl₃ with N(CH₂CH(CH₃)OH)₃ in the presence of triethylamine. The reaction of CpTi(OMe)₃ (8) with N(CH₂CH₂OH)₂(CH₂CHPhOH), erythro-N(CH₂CH₂OH)₂(CHPhCHPhOH), and N(CH₂CH₂OH)₂(CH₂CPh₂OH) gave cyclopentadienyltitanatranes 12–14. Compound 8 reacts with threo-N(CH₂CH₂OH)₂(CHPhCHPhOH) to give a mixture of threo-CpTi(OCH₂CH₂)₂(OCHPhCHPh)N and threo-MeOTi(OCH₂CH₂)₂(OCHPhCHPh)N. Slow hydrolysis of the latter product gave threo-[Ti₃O(OMe){(OCH₂CH₂)₂₋ (OCHPhCHPh)N} ₃]₂, which was studied by X-ray diffraction analysis. The crystal structures of 3 and 12 were also determined by X-ray diffraction analysis. The titanium coordination polyhedron in these complexes is a distorted trigonal bipyramid in which the equatorial positions are occupied by three oxygen atoms and the axial positions contain the N atom and the Cp group. The titanium—nitrogen distances (2.313(2), 2.291(2) Å in two independent molecules of 3 and 2.271(2) Å in compound 12) confirm the presence of Ti←N transannular interaction. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2736–2744, December, 2005.     

Optical bistability produced by resonant Joule's heating of semiconductors

The thermal hysteresis of Joule's absorption of infrared radiation in then-type semiconductor magnetoplasma is analysed. Such bistability is connected with the temperature dependence of the relaxation time of free electrons, their density being constant. The resonant Joule's absorption bistability of the pumping infrared wave near a Langmuir resonance of free electrons is discussed as well as the hysteresis cross-modulation of an infrared probing wave by means of a pumping microwave. The possibilities of smooth detuning of the hysteresis regime due to a magnetic-field control and low energy thresholds of these regimes are illustrated for InSb thin films in relatively weak magnetic fieldsH1–2 kG.     

Controlled ring‐opening homo‐ and copolymerization of ɛ‐caprolactone and d,l‐lactide by iminophenolate aluminum complexes: An efficient approach toward well‐defined macromonomers

The aluminum complexes containing two iminophenolate ligands of the type (p‐XC₆H₄NCHC₆H₄O‐o)₂AlR' (R′=Me ( 3, 4 ) or R′=O(CH₂)₄OCH=CH₂ ( 5, 6 ), X=H ( 3, 5 ), F( 4, 6 )) were synthesized and characterized by ¹H, ¹³C NMR spectroscopy, and X‐ray crystallography. The reaction of AlMe₃ with two equivalents of substituted iminophenols gave five‐coordinated {ONR}₂AlMe ( 3, 4 ) complexes. Subsequent reaction of these methyl complexes with unsaturated alcohol, HO(CH₂)₄OCH=CH₂, resulted in target compounds 5 and 6 in a good yield. It was shown that the complexes ( 3 ‐ 6 ) are monomeric in solution (NMR) and in solid state (X‐ray analysis). The catalytic activity of the complexes 5 and 6 towards ring‐opening polymerization (ROP) of ?‐caprolactone and d,l ‐lactide was assessed. Complex 5 showed higher activity as compared with 6 , while both of these catalysts induced controlled homo‐ and copolymerization to afford the macromonomers with high content of vinyl ether end groups (F_n > 80%) in a broad range of molecular weights (M_n = 4000–30,000 g mol^?1) with relatively narrow MWD (M_w/M_n = 1.1–1.5). © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 1237–1250     

New nanomolar negative modulators of AMPA receptors

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Search for tetrylene structures that can exhibit catalytic activity: a quantum chemical approach

We present the results of a quantum chemical study of a series of tetrylenes (silylenes, germylenes, and stannylenes), aimed at identifying structural and electronic factors affecting the width of the HOMO—LUMO energy gap. Compounds considered in this work contain atoms of Group 14 elements in both di- and tricoordinate states due to additional transannular interaction. They bear substituents bonded to the atom of the Group 14 element through atoms with and without lone electron pairs. It was found that tetrylenes stabilized by both additional transannular interaction and direct bonds between the atom of the Group 14 element and the heteroatom containing a lone electron pair (in this situation the ligand acts as n-donor) are characterized by wide HOMO—LUMO energy gaps, the gap in stannylenes always being narrower than in the related silylenes and germylenes. Localization of the HOMO and LUMO in certain tetrylenes is analyzed.

     

Syndiospecific polymerization of styrene in the presence of new titanium complexes with dialkanolamines: Titanocanes and bistitanocanes

The syndiospecific polymerization of styrene is studied in the presence of titanium complexes with dialkanolamines—bistitanocanes and titanocane—activated by individual MAO or the combined cocatalyst MAO/TIBA. It is shown that these catalysts are more active and stereospecific after their activation with the combined cocatalyst ([TIBA]: [MAO] ≤ 0.13) than that in the case of the activation with MAO: The activities of the catalysts are ≤18 and 9 kg PS/(mol Ti h), and the syndiotacticities of PS are ≤76 and 60%, respectively. Polymers synthesized in the presence of bistitanocanes are characterized by M _n ≤ 4.5 × 10⁴ and T _m ≤ 268°C and a narrow molecular-mass distribution (≤2.5).     

Isotope separation of the lanthanoid group elements by the method of two-step selective photoionization

Conclusions The experiments on the laser separation of the isotopes of the elements of the lanthanoid group have shown that obtaining isotopically pure materials by the method of selective photoionization is feasible.The data obtained are necessary for the planning of experiments on LIS of rare-earth elements of significant weight.In conclusion, the authors express their gratitude to V. V. Arinin, M. N. Glasko, V. N. Markov for help with the experiments and to A. M. Prokhorov for constant interest and support.Translated from Trudy Ordena Lenina Fizicheskogo Instituta im. P. N. Lebedeva Akademii Nauk SSSR, Vol. 114, pp. 50–59, 1979