Synthesis and photophysical studies of novel 4-aryl substituted 2-phenyl-, 2-(fluoren-2-yl)- and 2-cymantrenylquinazolines

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Investigation of the catalytic activity of metal complexes fixed on a solid support. 10. Selective hydrogenation of allylbenzene in the presence of heterogeneous Pt-Sn-citrate complexes

New heterogeneous catalysts based on the complexes of platinum with tin(II) citrate were prepared. The catalysts exhibit high selectivity in the hydrogenation of allylbenzene to propylbenzene without increasing the rate of isomerization of the C=C bond. The activity of the complexes depends on the conditions and decreases with increase in the Sn:Pt ratio.N. D. Zelinskii Institute of Organic Chemistry, Russian Academy of Sciences, 117913 Moscow. St. Petersburg Technological Institute. Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 6, pp. 1287–1290, June, 1992.     

Hydrothermal synthesis,structures and magnetic properties of two new holmium(III) oxalato complexes

Two new holmium (Ho) oxalato complexes have been synthesized under hydrothermal conditions and structurally characterized. [Ho(OH)₂]₂(C₂O₄) (1) has a 3-D structure with Ho-(μ₃-OH) hydroxide layers connected by μ₄-bridging oxalate ligands forming a unique hybrid structure. Sr(H₂O)₄[Ho(C₂O₄)₂(H₂O)]₂·2H₂O (2) has a 3-D structure built through μ₂-bridging oxalate ligands connecting hexagonal Ho oxalate layers with hydrated Sr²⁺ ions in the channels. Different oxalate ligand arrangements around the metal ions control the structural alterations among the lanthanoid double oxalates even with similar formulas. Both structures have been discussed and compared to the existing lanthanoid oxalato complexes. In addition, their vibration modes, thermal stabilities, electronic structures, and magnetic properties have been further investigated and reported. Both 1 and 2 show the deviation of the magnetic behaviors from the Curie–Weiss law due to the crystal field effects.     

Stabilizing and Activating Nitrogen Catenates

The remarkably stable catenated hexa‐nitrogen chain in bis(benzotriazene‐4‐one) is structurally, theoretically, and spectroscopically characterized to illustrate the durability of the central N?N bond in this hexaazo chain. The reactions of this species illustrate the potential of these nitrogen catenates for the preparation of other condensed heterocycles, such as bispyrazolones, by thermal nitrogen exclusion or by trapping the single ring‐opened Dimroth intermediates. In these latter reactions, 2‐naphtholate anion condenses with bis(benzotriazene‐4‐one) to trap and retain a zwitterionic diazonium intermediate as an isolated diazo product, whereas transition metals ring effect ring‐extrusion of dinitrogen from the Dimroth intermediate to generate chelating σ‐aryls. The catenated nitrogen species can be stabilized by incorporating strong formal sp²?sp² N?N σ bonds with orthogonal orientations. Extending these stabilization and activation principles may allow these types of nitrogen catenates to be useful synthons for other polyaza species.     

Neutral and ionic dissociation patterns in hexacoordinate silicon chelates: a model nucleophilic substitution at pentacoordinate silicon

A model nucleophilic-displacement reaction coordinate at pentacoordinate silicon is demonstrated by neutral and ionic dissociation equilibria through a stable hexacoordinate complex.     

Thermodynamic Properties and Molecular Dipole Moments of Antimony Compounds from Quantum Chemical Evaluations

By the PM3 method, standard values of entropy, heats and Gibbs energies of formation and dipole moments of the molecules have been computed for a series of inorganic and organic antimony compounds. Linear dependences P exper = bP theor (where P is any of the mentioned properties) have been stated, allowing a priori evaluation of thermodynamic characteristics and molecular dipole moments of Sb-containing substances. It has been concluded that triphenylstibinedichloride in benzene solution, as well as triphenylstibinehydroxychloride in dioxane medium, exist in the form of trigonal bipyramid with two axial chlorine and oxygen atoms.