Reactions of Magnesium and Titanium Alkoxides. Preparation and Characterization of Alkoxy-Derived Magnesium Titanate Powders and Ceramics

The interaction between magnesium and titanium alkoxides is studied in order to chose the best precursors for synthesis of MgTiO₃. No reaction between magnesium and titanium methoxides and isopropoxides occurs. The solubility diagrams for Mg(OR)₂-Ti(OR)₄-ROH, R = Et,-Bu at 20°C are studied. Magnesium ethoxotitanates of variable composition Mg_nTi_4-n (OEt)_16-2n2nEtOH (n=2.0-0) which are structural analogs of Ti₄(OR)₁₆ (R = Me, Et) are isolated. This is a quite unusual example of statistical distribution of heteroatoms in molecular structures of metal alkoxides. Among the systems of metal alkoxides with simple aliphatic radicals only Mg(OBu)₂-Ti(OBu)₄-BuOH gives a convenient precursor for the synthesis of MgTiO₃. A simple scheme of preparation of magnesium titanate from the alkoxide solutions is suggested. The phase purity of MgTiO₃ is to a considerable extent dependent on the hydrolysis conditions. The alkoxy-derived magnesium titanate is obtained in the form of a uniform fine powder, it can be sintered into dense ceramics in the temperature range of 1140–1220°C which is 150–200°C lower in comparison with the conventional powders.     

Synthesis,structure, and rearrangements of new tricarbonylchromium complexes of substituted heptalenes

Reactions of 1,2,5,6,8,10-hexamethylheptalene (1) and its bond isomer, 1,4,5,6,8,10-hexamethylheptalene (2), with tricarbonylchromium complexes L{in3}Cr(CO){in3} (L=NH{in3} and Py) have been investigated. Thermodynamically less stable complex 1 exhibits higher reactivity with respect to Py{in3}Cr(CO){in3}/BF{in3} · Et{in2}O under the conditions of Öfele's reaction than complex2. At 10–30 °C, the Cr(CO){in3} group is coordinated to the asymmetrically substituted ring, which is accomplished by the shift of double bonds in the ligand, to afford tricarbonyl-[1,4,5,6,8,10-hexamethyl-{su6}-(10a, 1–5)heptalene]-chromium (6) as the only mononuclear complex. Under more drastic conditions (Raush's reaction, 80 °C),1 2 interconversion proceeds faster than the reaction of individual bond isomers with coordinatively unsaturated hot particles (solv){inn}Cr(CO){in3}. In this case, all of the four possible isomeric mononuclear complexes (6–9) and two binuclear complexes (10 and 11) are formed. The structures of complexes 6–11 have been studied by NMR and mass spectrometry, the structure of6 has been established by X-ray diffraction analysis. Heating a solution of6 in octane at 115 °C results in the isomerization of6 into complex7 through the intracycle 1,2-shift of the Cr(CO){in3} group and also in its conversion into complex8, which is the first example of interring {su6}{su6}-haptotropic rearrangement in nonplanar seven-membered -systems.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2220–2226, December, 1994.We would like to thank N. S. Kulikov for measuring mass spectra and L. A. Aslanov for helpful discussion of the results of X-ray diffraction analysis.The Research Group from the Moscow State University gratefully acknowledges the support of this work by the International Science Foundation (Grant No. MQ 5000) and the Russian Foundation for Basic Research (Project No. 94-03-08325).     

Synthesis of dibenzocymantrene derivatives (η5-9-RC13H8)Mn(CO)3 (R = Ph and But). Crystal structure of (η5-9-PhC13H8)Mn(CO)3

⁵-Fluorenyl complexes of manganese (⁵-9-RC₁₃H₈)Mn(CO)₃, where R = Ph (1) and But (2), have been prepared and characterized for the first time. The structure of complex1 has been established by X-ray structural analysis.Yu T. Yanovsky deceased in 1995.Translated fromIZvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 199–203, January, 1996.     

Metallocenes in oxidative-reductive transmetallzation with bis[tris(pentafluorophenyl)germyl]mercury

Conclusions The oxidative-reduction transmetallation reaction between bis[tris(pentafluorophenyl)-germyl]mercury and the dicyclopentadienyl derivatives of various metals can yield ionic multinuclear ate-type complexes, covalent compounds with a metal-metal bond, or ionic complexes that form by transfer of a cyclopentadienyl anion from the central metallocene atom to mercury.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2548–2555, November, 1986.The authors thank N. Walker and D. Stuart for providing the DIFABS program.     

酚醛型吸附树脂在非水体系中对吡啶和N,N-二甲基苯胺的吸附性能研究

研究了酚醛型吸附树脂JDW 2在非水体系中对吡啶和N ,N 二甲基苯胺的静态吸附 .由实验结果推论正己烷中树脂对吡啶和N ,N 二甲基苯胺的吸附是以氢键吸附机理为主进行的 ,JDW 2酚醛型吸附树脂在正己烷中 ,等温吸附吡啶和N ,N 二甲基苯胺的平衡吸附数据符合Langmuir方程 ,相关系数在 0 99以上 ,因此 ,酚醛型吸附树脂在正己烷中吸附吡啶和N ,N 二甲基苯胺属单分子层吸附 ;同时对非水体系中乙醇或乙酸乙酯的含量对树脂吸附吡啶和N ,N 二甲基苯胺的影响进行了研究     

Electrochemical study of allylbenzene and allylcyclohexadienyl complexes of ruthenium

Cyclic voltammetry has been used to study the electrochemical behavior of RuCl(³-C₃H₅)(⁶-C₆H₆) (1), [Ru(PPh₃) · (³-C₃H₅)(⁶-C₆H₆)]BF₄ (2), and Ru(PPh₃)· (³-C₃H₅)(⁵-C₆H₇) (3); the latter was prepared by reacting2 with LiAlH₄. The reduction of1 and2 gives the 19-electron complexes1 ^–. and 2^·, whereas oxidation of3 gives the 17-electron complex3 ^+·. The reactivities of1 ^–·,2 ^·, and3 ^+· are discussed.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1126–1128, June, 1993.     

New Stable Germylenes,Stannylenes, and Related Compounds II. Bis(butylthio)tin(II) and ate-Complexes [(Me3Si)3CE(μ-SBu)2Li(THF)2] (E = Ge,Sn). Synthesis and Structure

By reaction of Me₃SiSBu with anhydrous tin(II) chloride bis(butylthio)tin was obtained that exemplified a coordination polymer [Sn(SBu)₂] _n , whose elementary unit contained according to X-ray diffraction study three independent four-membered rings Sn₂S₂ of unusual geometry. It was demonstrated that polymeric thiolates [E(SBu)₂] _n (E = Ge, Sn) readily reacted with TsiLi (Tsi = C(SiMe₃)₃) in a mixed solvent ether THF affording in a good yield ate-complexes [(Me₃Si)₃CE(-SBu)₂Li(THF)₂]. Both complexes contain a four-membered ring in a butterfly conformation where the lithium atom is symmetrically bonded to both sulfur atoms, and the coordination polyhedra of Ge and Sn atoms may be regarded as distorted tetrahedra AB₃X, where one of coordination places is occupied by unshared electron pair. The structure of the ate-complexes observed in a crystal is conserved also in solution of nonpolar solvents.     

Molecular structure of 6-(N,N-dimethylamino)fulvene from a joint gas-phase electron diffraction and quantum-chemical study

The molecular structure of 6-(N,N-dimethylamino)fulvene was studied by gas-phase electron diffraction and quantum-chemical methods (HF/6-31G(d), MP2/3Z, MP2/4Z, density functional theory with the B3LYP/6-31G(d) and PBE/3Z functionals). Pronounced flattening of the nitrogen atom and equalization of the intracyclic C—C bonds were found to be a consequence of the electron delocalization in the molecule.     

Heteroorganic betaines. 8. Synthesis and structures of silicon- and germanium-containing organoarsenic betaines R13As+—CR2R3—EMe2—S– (E = Si,Ge)

The reactions of ylides R¹ ₃As=CHR² with hexamethyl-2,4,6-trisila- and hexamethyl-2,4,6-trigermatrithiacyclohexanes afforded betaines R¹ ₃As⁺—CHR²—SiMe₂—S^– (2) (R¹ = Et; R² = Ph (a), Me₃Si (b); R¹ = R² = Ph (c)) and Et₃As⁺—CH(SiMe₃)—GeMe₂—S^– (3), respectively. Betaines 2a,b and 3 were characterized by multinuclear NMR spectroscopy. According to the X-ray diffraction data, in the crystals the As⁺—C—E—S^– main chain (E = Si or Ge) of molecules 2a,b and 3 adopts a twisted cis conformation due to strong intramolecular Coulomb interactions between the anionic and cationic centers. The equilibrium geometries of isolated molecules 2a and 3, which were calculated within the framework of the density functional theory (the PBE functional, the TZ2P basis set), are in qualitative agreement with the X-ray data. In solutions, betaines 2a (in the absence of Li salts) and 2c (in the presence of LiBr) selectively decomposed according to the Corey—Chaykovsky reaction, which was accompanied by elimination of R₃As and, probably, the intermediate formation of silathiirane. The subsequent transformation of the latter afforded 2,2,4,4-tetramethyl-5-phenyl-2,4-disila-1,3-dithiolane.     

Molecular geometry and electronic structures of stable organic derivatives of divalent germanium and tin [(\operatorname{Me} _3 \operatorname{Si} )_2 \operatorname{N} {\kern 1pt} ---{\kern 1pt} Me_2 ]_n (M = Ge, n = 1; M = Sn, n = 2): a theoretical study

The molecular geometry and electronic structure of stable organic derivatives of divalent germanium and tin, [(Me₃Si)₂N-M-OCH₂CH₂NMe₂]_n (M = Ge (4), n = 1; M = Sn (5), n =2) and their isomers with broken (4a, 5a) and closed (4b, 5b) intramolecular coordination bonds M←NMe₂, were studied by the density functional (PBE/TZ2P/SBK-JC) and NBO methods. Factors responsible for stability of their dimers 4c and 5c were established. Dimerization of 5b in the gas phase is a thermodynamically favorable process (ΔG ⁰ = ?2.1 kcal mol^?1) while that of 4b is thermally forbidden (ΔG ⁰ = 10.1 kcal mol^?1), which is consistent with experimental data. The M←NMe₂ coordination bond energies, ΔE ⁰, were found to be ?5.3 and ?8.6 kcal mol^?1 for M = Ge and Sn, respectively. NBO analysis showed that the metal atoms M in molecules 4 and 5 are weakly hybridized. The lone electron pairs of the M atoms have strong s-character while vacant orbitals of these atoms, LP* M, are represented exclusively by the metal np_z-AOs. The strongest orbital interactions between subunits in dimers 4c and 5c involve electron density donation from the lone electron pairs of oxygen atoms (LP O) to the LP* M orbitals.