Showing papers by "Vadim G. Kessler published in 1998"

Anodic oxidation of molybdenum and tungsten in alcohols: isolation and X-ray single-crystal study of side products

Abstract: The study of the side products of the anodic dissolution of molybdenum and tungsten metals in alcohols in the presence of LiCl showed them to be [LiMo2O2(OMe)7(MeOH)] 1 in the case of MeOH and [LiMo2O4(OEt)5(EtOH)] 2 in EtOH. Treatment of 2 with an excess of PriOH gave [LiMo2O4(OPri)5(PriOH)] 3, the structure of which was confirmed by a study of [{LiMo2O4(OPri)4(OC2H4OMe)}2] 4, the product of partial substitution of OR groups in 3 by 2-methoxyethoxide ligands. Reaction of 2 with an excess of MeOC2H4OH led to an equimolar mixture of [MoO2(OC2H4OMe)2] and [LiMoO2(OC2H4OMe)3] 5. In PriOH a crystalline product identified as [Mo6O10(OPri)12] 6 was isolated. Anodic oxidation of tungsten in MeOH gave a mixture of homometallic W(OMe)6 and [WO(OMe)4]. Electrosynthesis in EtOH gave as major product an amorphous glass-like mass {after separation of crystalline [WO(OEt)4] by filtration and subsequent drying of the filtrate in vacuo}. Treatment of the latter with an excess of HOC2H4OMe led to crystallization of [{LiWO2(OC2H4OMe)3}2· 2Li(HOC2H4OMe)2]2+[W6O19]2– 7. Complexes 1, 4 and 7 were characterized by X-ray single-crystal studies. A GLC-mass spectrometric study of the composition of organic side products indicated that the processes were associated with formation of ethers, alkyl halides, aldehydes or ketones and their derivatives. The nature of the possible side reactions was deduced on the basis of the data obtained.

Molecular Precursor Role in the Synthesis of ZrMVI2O8, MVI = Mo, W: Isolation and Properties of Zr3Mo8O24(OiPr)12(iPrOH)4

Abstract: The studies of zirconium isopropoxide solvate, Zr(OiPr)4·iPrOH(I), interaction with molybdenum oxoisopropoxide in different solvents (HOiPr, hexane) revealed I to be the only isolable crystalline product in alcohol In hexane I crystallized from Zr-rich solutions (up to Zr : Mo = 1 : 2 ratio) From the solutions with Zr : Mo = 1 : 2 ratio repeatedly dried in vacuo and subsequently redissolved in hexane, the crystallization of Zr3Mo8O24(OiPr)12(iPrOH)4(II) occurred slowly with 12% yield II can be recrystallized from hexane, but is destroyed by iPrOH which causes the formation of I Thermal decomposition of II in air at 800°C (2 h) gives a single phase ZrMo2O8(III) Hydrolysis studies of hexane solutions, prepared in a manner analogous to those, from which II was obtained, showed that single-phase samples of III could be obtained when a thin layer of solution was left for hydrolysis and evaporation of solvent in a moist air and then annealed at 800°C (2 h) The same kind annealing of a xerogel, obtained by hydrolysis with water solutions in iPrOH and subsequent drying at 100°C gave a complex mixture of phases where III was not even the major component No Zr-W complex was isolable under analogous conditions From the xerogel, obtained by hydrolysis with H2O/iPrOH, ZrO2 and WO3 crystallized separately on heating Only traces of ZrW2O8(IV) were obtained along with individual oxides when 1% water in ether was applied for hydrolysis Molecular precursor is therefore crucial for obtaining III, IV

Synthesis of organic-inorganic hybrid materials by incorporation of molybdenum and tungsten hydrated oxides in polymers

Abstract: In order to obtain new organic-inorganic hybrid materials the method exploiting the phenomenon of polymer crazing was investigated. Polypropylene and polyethyleneterephtalate films were subjected to crazing to achieve high porosity. Incorporation of hydrated oxides of Mo and W in porous polymer matrix was performed by hydrolysis of alkoxides in pores using counterflow diffusion technique. It was shown that peculiarities of the hydrolysis of the initial compounds affect significantly the distribution of substances inside porous polymer matrix and the possibility of accumulation of inorganic component inside the film. Mo matter in contrast to W is easily incorporated in the polymer matrix to form a well-defined layer. These samples demonstrated high photosensitivity.