New organogermanium cations [RGe(OCH2CH2NME2)2]+ with intramolecular N→Ge coordination bonds

New organohalogermanes RGe(OCH₂CH₂NMe₂)₂X (R = Ph, X = I (5); R = Me, X = Cl (6) or I (7)) with an intramolecular N→Ge coordination bond were synthesized. According to the ¹H and ¹³C NMR spectroscopic data, iodides 5 and 7 exist in solution as ionic compounds with the pentacoordinated germanium atom. In solution of compound 4 (R = Ph, X = Cl), there is an equilibrium between the ionic and covalent forms. The equilibrium shifts toward the ionic form with increasing solvent polarity or temperature. In solution, chloride 6 is a covalent compound. The structures and relative stabilities of different isomers of compounds 4–7 were studied by quantum chemical calculations at the density functional level of theory. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 892–900, May, 2007.     

Can Sn(OCH2CH2NMe2)2 behave as a stannylene? Equatorial-axial isomerism in the tin(II)-iron(0) complex (Me2NCH2CH2O)2Sn-Fe(CO)4

Equatorial-axial isomerism of the tin(II)-iron(0) complex (Me2NCH2CH2O)2Sn-Fe(CO)4 (), which indicates that the free Sn(OCH2CH2NMe2)2 () ligand can behave as a stannylene, has been revealed and studied by NMR and IR spectroscopy in solution as well as by Raman spectroscopy and X-ray diffraction analysis in the solid-state.     

Investigation of Sr uptake by birnessite-type sorbents from seawater

Sorption of micro- and microamounts of Sr from seawater has been studied using granulated Na-birnessite. Distribution coefficients of ⁹⁰Sr in the natural seawater are 0.8–1.2?×?10³ ml g^?1, in the model seawater they are 1.6–1.8?×?10³ ml g^?1. Application of Na-birnessite was shown to be prospective in sorption–desorption–regeneration regime. In dynamic sorption conditions, over 150 bed volumes of seawater can be purified till 5% breakthrough occurs at feed rate 10 BV h^?1. Na-birnessite can be used for ⁹⁰Sr radionuclide removal from liquid radioactive wastes containing seawater.

     

Estimates for weak solutions of a nondiagonal parabolic system of two equations

Estimates for the L ^∞-norms of weak solutions are obtained for a model nondiagonal parabolic system of nonlinear differential equations with matrix of coefficients satisfying special structure conditions. A technique based on estimating the certain function of unknowns is employed to this end.     

Hölder continuity of the solutions of a nondiagonal parabolic system of equations with <Emphasis Type="Italic">p</Emphasis>-laplacians

We prove the Hölder continuity of the solutions of the Dirichlet problem for a nondiagonal parabolic system of equations in divergence form whose leading parts are modeled by the p-Laplacians.     

In search for a pentacoordinated monoorgano stannyl cation

Alkylation of Sn(OCH₂CH₂NMe₂)₂ (1) by MeI or MeOTf leads to a mixture of quaternary ammonium salts by alkylation of the NMe₂ moiety. Reaction of Sn(acac)₂ (2) with MeOTf gives unexpected redistribution product Sn(acac)OTf (3), which is a rare example of mono acetylacetonato tin (II) derivatives. Pentacoordinated monoorgano stannyl cation was generated by salt metathesis from PhSn(OCH₂CH₂NMe₂)₂Cl (5) and Ag[Al(OCH(CF₃)₂)₄] or Ag[B(C₆F₅)₄]. This cation was not isolated due to its strong electrophilic nature. It abstracts substituents from aluminate and borate weakly coordinating anions (WCAs) leading to redistribution products [Al[OCH(CF₃)₂]₂OCH₂CH₂NMe₂]₂ (6) and [Ph(C₆F₅)Sn(OCH₂CH₂NMe₂)₂][H₂OB(C₆F₅)₃] (9), respectively. Structures of 3 and 6 were established by single-crystal X-ray diffraction analysis.     

The maximum and comparison principles for a system of two equations

We propose a method of generalizing the well-known maximum and comparison principles to nondiagonal parabolic systems of second order nonlinear differential equations. Under consideration are the cases of Dirichlet and Neumann problems. We also present some examples of the systems that this method applies to.     

Effect of the Solvent Composition on the Content of the Crystalline Phase and Melting Temperature of Paraffin Waxes

Russian Journal of Applied Chemistry - The results of a study of melting the commercial waxes in the composition of asphaltene-resin-paraffin deposits and for comparison of petroleum waxes in...     

Germanium carboxylates: the first X‐ray diffraction study of germanium(II) dicarboxylate and germanium(IV) tetracarboxylate

Germanium(II) dipropionate (1) has been synthesized and its crystal structure, as well as that of germanium(IV) tetrapropionate (2), has been determined. By contrast to monomeric 2 with monodentate propionate ligands, compound 1 is associated, forming a cyclotetramer [Ge(O₂CEt)₂]₄ (1a) via intermolecular dative C?O → Ge interactions. Copyright © 2005 John Wiley & Sons, Ltd.     

Classical solvability of a parabolic system of two nonlinear equations

We study the complete regularity of solutions of a nondiagonal parabolic system of quasilinear second-order differential equations in divergence form assuming that the coefficients are sufficiently slowly varying functions of their arguments and the off-diagonal terms in the coefficient matrix are sufficiently small. To this end, we use a method based on the successive approximation to the solution by smooth functions with the use of Schauder estimates at each step.