Charge control of phenol complexation with unsaturated compounds containing group IVB organometallic substituents. Interpretation of NMR spectra of acetylenic derivatives

²⁹Si and ¹¹⁹Sn chemical shifts in the NMR spectra of acetylenic derivatives Me₃ECCX (E = Si or Sn; X — organic substituents) and shifts of frequencies () of stretching vibrations of OH groups in the IR spectra of phenol when hydrogen-bonded to these compounds have been analyzed. In each of two series (E = Si or Sn), the and values are connected by a linear relationship; this indicates that there is virtually no effect of the magnetic anisotropy of the X substituents on the chemical shifts. It has been established that the shifts of the frequencies and the ²⁹Si and ¹¹⁹Sn chemical shifts are the relative characteristics of the effective negative charge on the carbon atoms of the triple bond in Me₃ECCX compounds.For the previous communication of this series, see Ref. 1.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2069–2073, December, 1993.     

Bulk propylene polymerization in the presence of ansa-metallocenes of C 2 and C 1 symmetries: From a rigid thermoplastic to elastomeric stereoblock polypropylene

Bulk propylene polymerization in the presence of ansa-metallocenes with C ₂ and C ₁ symmetries has been studied. The catalytic activity, polymerization kinetics, and the molecular weight of polypropylene (PP) depend strongly on catalyst formation conditions. Mixtures of rac and meso isomers of metallocenes make it possible to rapidly produce a high-molecular-weight isotactic PP with high stereoregularity and mechanical characteristics and thus skip the stage of the isolation of pure rac isomer in the catalyst synthesis. The ability of triisobutylaluminum to serve as a cocatalyst is studied for ansa-metallocenes of C ₁ symmetry. In this case, the molecular weight of PP is higher, indicating that organoaluminum compounds participate in chain termination reactions. An increase in the reaction temperature results in an increase in the stereoregularity and crystallinity of PP. Polypropylene synthesized using ansa-metallocenes of C ₁ symmetry has good elastomeric properties.     

On the influence of a geothermal system on ground deformation during a volcanic eruption

The measurement of ground deformation during a volcanic eruption is one of the main tools for the monitoring of active volcanoes. The deformation is caused by processes that are occurring in the chamber–conduit system, as well as in the geothermal systems that are heated by ascending magma. The influence of the magma chamber and, to a lesser degree, of the conduit on deformation in host rocks is sufficiently well known theoretically, but no studies have been made to investigate the effects of a hydrothermal system on measurable ground deformation during a volcanic eruption. We made a comparative study of the ground deformation due to two deformation-initiating sources: a fissure conduit with a specified excess pressure and a hydrothermal system that was heated by magma flow. We show that the vertical deformation due to the activity of a geothermal system can exceed that due to magma flow by factors of several times. The spatial distributions of the deformation are also substantially different. The vertical displacement due to a geothermal system has its maximum above the fissure conduit, while when the pressure varies in the conduit it induces a local subsidence of the ground; the maximum ground uplift is at a distance of approximately twice the depth to the top of the conduit. The influence of the geothermal system should be incorporated in interpretations of data that come from the monitoring of active volcanoes.     

Catalytic [2+2]-cycloaddition of 3,3-disubstituted cyclopropenes to norbornene and norbornadiene

Conclusions 3,3-Dialkyl(cycloalkyl)cyclopropenes react with norbornene and norbornadiene at –20°C in the presence of complexes of CuCl with (PhO)₃P or Ph₃P exclusively by [2 + 2]-cycloaddition, giving the corresponding exo,trans-tetracyclo[5.2.1.0^2,6.0^3,5]decanes (or decenes) in yields of 60–94%, the tricyclohexane cyclodimers being obtained in yields of 5–25%.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1534–1540, July, 1987.     

Pyran,its analogs,and related compounds

The effect of amines (benzylamine, N,N-dimethylethylenediamine, and ethylenediamine) on the tert-butyl ester (I) and tert-butyl amide (II) of chromone-2-carboxylic acid was studied. In contrast to the sterically unhindered derivatives of chromone-2-carboxylic acid, I and II do not undergo amidation or transamidation by reaction with the amines but are converted directly to pyran-ring-opening products. In the case of ethylenediamine, further intramolecular cyclization also occurs to form 5-(o-hydroxyphenyl)-7-carboxy-1,4-diaza-4,6-cycloheptadiene derivatives (VII and IX).See [6] for communication XXXVIII.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 17–21, January, 1971.     

Synthesis of propylene-ethylene copolymers in liquid propylene using <Emphasis Type="Italic">ansa</Emphasis>-metallocenes of the <Emphasis Type="Italic">C</Emphasis><Subscript>1</Subscript> symmetry

The copolymerization of ethylene with propylene in the liquid propylene initiated by ansa-metallocenes of the C ₁ symmetry, rac-[1-(9-η⁵-fluorenyl)-2-(5,6-cyclopenta-2-methyl-1-η⁵-indenyl)ethane]zirconium dichloride and rac-[1-(9-η⁵-fluorenyl)-2-(5,6-cyclopenta-2-methyl-1-η⁵-indenyl)ethane]hafnium dichloride, activated by methylaluminoxane has been studied. Triisobutylaluminum has been used as a cocatalyst. The propylene-ethylene copolymers thus prepared contain 5–60 mol % ethylene units. The reactivity ratios have been measured. In the case of the zirconocene-based catalyst, the molecular mass of the copolymers decreases with an increase in the content of ethylene units. The reverse situation is observed in the case of the hafnocene-based catalytic system. The copolymers are characterized by the low T _g values (down to ?45°C). Incorporation of a small amount of ethylene units (5 mol %) results in a rise in the elastomeric behavior of the polymers.     

Thermodynamic properties of 1,3-dimethylsilatrane and 1-(2-cyanoethyl)silatrane

The heat capacities of 1,3-dimethylsilatrane and 1-(2-cyanoethyl)silatrane were measured, and their thermodynamic functions were calculated. In the intervals 12–205 and 215–315 K, the heat capacity of 1,3-dimethylsilatrane smoothly varies with temperature. A reproducible thermal effect is observed at ～315 K, and a G-type transition, in the range 205–215 K. 1-(2-Cyanoethyl)silatrane shows no anomalies in the examined temperature range. Above 260 K, the rate of the growth of the heat capacity with temperature increases.