Nataliya Turova

Synthesis, crystal and molecular structure of calcium oxo ethoxide, [Ca6(µ4-O)2(µ3-OEt)4(OEt)4]·14EtOH

The hexanuclear complex of calcium oxo ethoxide ethanol solvate, [Ca6O2(OEt)8]·14EtOH 1 has been isolated after the prolonged refluxing of an ethanol solution of calcium ethoxide in the presence of the oxygen in air and studied by X-ray diffraction; the metal-oxygen framework is built of two [Ca4O4] cubes sharing a common [Ca2O2] face, which involves both oxo groups.

The synthesis and X-ray crystal structure of molybdenum oxomethoxide [MoO(OMe)4]2

MoO(OMe) 4 has been prepared by anodic oxidation of molybdenum metal in anhydrous methanol containing LiCl as an electrolyte. The X-ray single crystal study showed the complex to consist of pseudo-centrosymmetric dimeric molecules, [MoO(OMe) 3 (μ-OMe)] 2 . The general effect of the M(μ-OR) 2 M ring upon the arrangement of bonds with increased multiplicity is discussed in this and related molecules.

Scandium alkoxides: the first mixed-ligand alkoxides containing the [M5O(OR)8] core, scandium alkoxoaluminates

Abstract The electrochemical synthesis of Sc(OMe)3 (1), Sc(OEt)3 (2) and Sc5O(OPri)13 (3) was carried out via anodic oxidation of scandium metal in aliphatic alcohols. X-ray single crystal study showed 3 to be analogous to the known isopropoxides of Y, Er, Yb and In. The interaction of 3 with excess ROH (R=Me, Et, Bun, Bus, But) gives non-volatile amorphous 1, 2 and Sc(OBun)3 (4), and volatile Sc5O(OBus)13 (5) and Sc5O(OPri)8(OBut)5 (6). Oxoalkoxides Sc5O(OPri)8(OR)5 (R=Bun 7, Me 8) were obtained on reaction of 3 with n-ROH in 1:5 ratio. The mass spectral study shows 5 is an individual compound, whereas 6–8 in the gas phase consist of a number of aggregates with different extents of substitution for OPri groups, Sc5O(OR)n(OPri)13−n: for R=But n≤5, for R=Bun n≤8, and for R=Me n≤12. The maximal intensity in the spectrum of 6 is observed for Sc5O(OPri)10(OBut)2+, and in the spectra of 7 and 8 for Sc5O(OPri)12−n(OBun)n+, n=4, 5, and Sc5O(OPri)9(OMe)3+ respectively. The presence of the Sc5O(OMe)12+ ion in the spectrum of 8 indicates the possibility of replacing all the OPri in the pentanuclear core and demonstrates the existence of a ‘volatile scandium methoxide’ in the gas phase. Study of the complex formation of Sc(OR)3 with Al(OR)3 has shown that 2 and 4 form volatile Sc[Al(OR)4]3, R=Et 9, Bun 10, while 3 does not react under these conditions. Sc[Al(OPri)4]3 (11) can be obtained only on exchange reaction of ScCl3 with KAl(OPri)4. The results obtained indicate rather high stability of the [Sc5O(OR)8] core for primary and secondary R.

Synthesis, X-ray structure and thermal decomposition of lanthanum [dioxoisopropoxomolybdate] [La2Mo4O4(μ4-O)4(μ-OPri)8(Opri)6]

Abstract The reaction of lanthanum isopropoxide with the isopropoxide of molybdenum(VI), MoO(OPr i ) 4 , in 1:2 molar ratio in hexane, leads to the formation of the mixed-metal hexanuclear complex La 2 Mo 4 O 4 ( μ 4 -O) 4 ( μ -OPr i ) 8 (OPr i ) 6 ( 1 ), formally derived from the dioxomolybdenum species MoO 2 (OPr i ) 2 . The molecule of 1 contains an unusual tetragonal bipyramidal La 2 Mo 4 metal core supported by four tetradentate oxobridging ligands binding two neighbouring molybdenum and both lanthanum atoms each. Complex 1 readily decomposes either in solution in iso-propanol or on heating in vacuo to 90°C. The mechanism of the latter process is discussed.

Synthesis and crystal structure of the double barium–titanium isopropoxide [Ba4Ti4(µ4-O)4(µ3-OR)2(µ-OR)8(OR)6(ROH)4][Ba4Ti4(µ4-O)4(µ3-OR)2(µ-OR)9(OR)5(ROH)3]

An X-ray structural study of the crystals isolated from the solutions obtained by the reaction of Ba metal with Ti(OPri)4 in isopropyl alcohol has been carried out; the crystals of the compound, which is a precursor for the synthesis of BaTiO3, contain molecules of two different kinds [Ba4Ti4O4(OR)16(ROH)4] and [Ba4Ti4O4(OR)16(ROH)3], where R = Pri.

SYNTHESIS, CRYSTAL AND MOLECULAR STRUCTURE OF A NEW HETEROMETALLIC OXO-2-METHOXYETHOXIDE, BAMO2O5(OC2H4OME)4(HOC2H4OME)

Abstract The colorless needle-shaped crystals of a new heterometallic 2-methoxyethoxide, BaMo2O5(OC2H4OMe)4(HOC2H4OMe) (1), have been obtained by the saturation of barium 2-methoxyethoxide solution in 2-methoxyethanol with the crystalline MoO2(OC2H4OMe)2. The precipitation started when the Ba:Mo ratio achieved a 1:2 value and the precipitate formed contained BaMoO4 as an admixture thus indicating that the formation of oxo species led partially even to formation of inorganic molybdates. Molecules of 1 involve the metal–oxygen framework quite typical of trinuclear homo- and heterometallic alkoxide species. The rather high coordination number of the barium atom (10) and the lengths of the observed interatomic distances permit to suggest that this atom in 1 forms predominantly ionic bonds and, therefore, complex 1 can be formulated as [Ba(HOC2H4OMe)]2[Mo2O5(OC2H4OMe)4]2−.

The synthesis, crystal and molecular structures of bimetallic ethoxides of barium and titanium, and calcium and titanium: [M{Ti2(µ3-OEt)2(µ-OEt)3(OEt)4}2](M = Ca, Ba)

The X-ray single-crystal studies of [M{Ti2(OR)9}2](M = Ca, Ba; R = Et) obtained from EtOH solutions in 1 : 4 metal–titanium ratios show that these complexes, both in the solid state and in solution, are composed of symmetric molecules, in which the central eight-coordinated metal atom is bound to two face-sharing bioctahedral [Ti2(OR)9] groups.

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

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.

On the structure of heterometallic methoxide Li2(WO)2(OMe)10·MeOH

Abstract The crystalline Li2(WO)2(OMe)10·MeOH (I) is formed as a side product in the process of anodic oxidation of tungsten in methanol in the presence of LiCl, which is used as a conductive additive. The structure of I as determined by the X-ray diffraction (XRD) method features infinite chains made up of two alternating tetranuclear species [Li2(WO)2(OMe)10] (A) and [Li2(WO)2(OMe)10(MeOH)2] (B), linked via LiOW bridges involving the Li atom belonging to fragment A and tungstenyl group from fragment B. Each fragment occupies a special position in the crystallographic inversion center and has a metal–oxygen framework. All tungsten atoms have octahedral coordination, whereas all lithium vertices have five-coordinated trigonal bipyramidal environments. The H-bonds of the (A)WO…HOMe(B) type in the crystal of I provide the links between the A and B fragments belonging to the different chains.

The structure of the LiOMe·2MeOH crystal solvate. A new structural type for tetrameric alkoxides

The solvate LiOMe·2MeOH (1) was isolated from a solution of LiOMe in MeOH, its tetrameric unit [Li4(μ-OR)4(μ-ROH)2(ROH)4]·2ROH may be described as two distorted squares [Li2(μ-OR)(μ-ROH)], linked by bridging alkoxy groups and two hydrogen bonds; 1 easily loses the solvate alcohol yielding polymeric LiOMe.