- Synthesis and X-ray single crystal study of the bi- and trimetallic alkoxides of molybdenum(VI) and tantalum, Mo2Ta4O8(OMe)16, Mo4Ta4O16(O(i)Pr)12 and LiMo4Ta3O14(O(i)Pr)9(OC2H4OMe)3
-
The partial hydrolysis of a mixture of molybdenum and tantalum methoxides (Mo:Ta = 1:2) with stoichiometric amounts of water yields a new bimetallic complex Mo2Ta4O8(OMe)16 (I) on crystallization from toluene. The molecules of I appear to be a combination of two MoO2(O(i)Pr)2 units with the earlier described Ta4O4(O(i)Pr)12 core. The thermal reduction of a mixture of MoO(O(i)Pr)4 and Ta2(O(i)Pr)10 (in a 1:1 Mo:Ta ratio) followed by oxidation of the products by dry oxygen, provides access to Mo4Ta4O16(O(i)Pr)12 (II). The same procedure, using LiMo2O4(O(i)Pr)4(OC2H4OMe) instead of MoO(O(i)Pr)4, yielded trimetallic LiMo4Ta3O14(O(i)Pr)9(OC2H4OMe)3 (III) in minor yields. The molecular structure of II can be described as a distorted cube, the corners of which are occupied in turn by [((i)PrO)3Ta(μ-O)3] octahedra and [MoO(μ-O)3] tetrahedra sharing common vertexes. The molecular structure of III can be derived from that of II by replacing one [((i)PrO)3Ta(μ-O)3] octahedron with an [Li(μ, η2-OC2H4OMe)3] trigonal prism (the coordination number of the three Mo atoms is then increased to six). (C) 2000 Elsevier Science Ltd.
- Johansson, Anders,Kessler, Vadim G
-
-
Read Online
- Heterometal Alkoxides of Tantalum: Lithium, Magnesium, and Barium Alkoxotantalates
-
The formation of bimetal alkoxides of tantalum with Li, Mg, and Ba was studied by constructing solubility diagrams for the M(OR)n-Ta(OR)5-ROH (M = Li, Mg, Ba; R = Me, Et, i-Pr, n-Bu) systems at 200C. LiTa(OR)6 (R = Mc, Et, n-Bu), BaTa2(OPr-i)12 . 2i-PrOH, and MgTa2(OR)12 . 2ROH (R=Et, i-Pr) complexes were found to exist in the crystalline state. Their crystallization branches are located in the Ta(OR)5-rich regions relative to compositions of the complexes. Crystalline alkoxotantalates do not form in the systems involving Mg(OMe)2, Ba(OEt)2, and Mg(OBu-n)2. However, the location of the solubility curves of MII(OR)2 suggests the formation of MII : Ta = 1 : 2 complexes in solution, and this was confirmed by electrical conductivity and viscosity measurements on isomolar series of solutions. No complexes form between barium and tantalum butoxides. Fragments of MIITa2(OR)12 (R=Me, Et, i-Pr) and [LiTa(OR)6]2 molecules were detected massspectrometrically (the latter result from the oligomerization of polymeric chains existing in the solid phase). Long-term storage in alcoholic solutions causes the decomposition of the alkoxotantalates yielding crystalline LiTa9O13(OEt)20 · 2ROH, [LiTaO(OEt)4(EtOH)]2, [BaTaO(OMe)5(MeOH)2.5]4, [BaTaO(OEt)5(EtOH)1.5]4, and [MgTaO(OBu-n)5(n-BuOH)]4 oxoalkoxotantalates. The solvate LiOPr-i · 2i-PrOH and its behavior in i-PrOH were described for the first time.
- Tchebukov,Turova,Korolev,Belokon'
-
p. 1498 - 1508
(2008/10/08)
-
