Neven Strukan

A Series of Molybdenum(VI) Complexes with Tridentate Schiff Base Ligands

Mononuclear and polynuclear dioxomolybdenum(VI) complexes with Schiff base ligands have been prepared by the reaction of [MoO2(acac)2] with salicylaldehyde (1 and 4), 2-hydroxy-1-naphthaldehyde (2 and 5) and 2-hydroxy-3-methoxybenzaldehyde (3 and 6) with addition of appropriate amine. All prepared complexes of the general formulae [MoO2LD] and [MoO2L]n consist of cis-MoO22+ core coordinated by Schiff-base ligand (L) in a tridentate manner through two deprotonated hydroxyl groups and one imino nitrogen. The usual octahedral coordination around molybdenum atom is completed by monodentate solvent molecules D (methanol, ethanol or dimethylsulphoxide). All compounds were characterized by means of chemical analysis, IR spectroscopy, thermogravimetric analysis and some of them by X-ray crystallography (1a, 2c, 3a, 4c and 6c). Eine Reihe von Molybdan(VI)-Komplexen mit dreizahnigen Schiff-Basen-Liganden Ein- und vielkernige Dioxomolybdan(VI)-Komplexe mit Schiff-Basen-Liganden wurden durch Reaktion von [MoO2(acac)2] mit Salicylaldehyd (1 und 4), 2-Hydroxy-1-naphthaldehyd (2 und 5) und 2-Hydroxy-3-methoxybenzaldehyd (3 und 6) durch Zugabe von Amin hergestellt. Alle Komplexe der allgemeinen Formeln [MoO2LD] und [MoO2L]n enthalten die cis-MoO22+-Einheit, die durch die Schiff-Basen-Liganden dreifach durch zwei deprotonierte Hydroxyl-Gruppen und durch ein Imino-Stickstoffatom koordiniert ist. Die ubliche oktaedrische Koordination am Molybdanatom wird durch einzahnige Solvens-Molekule D (Methanol, Ethanol oder Dimethylsulfoxid) erganzt. Alle Verbindungen werden durch Elementaranalysen, IR-Spektren, thermogravimetrische Analysen und einige von ihnen durch Kristallstrukturanalysen (1a, 2c, 3a, 4c und 6c) charakterisiert.

Synthesis and structure of K2[HMo6VIVVO22(NH3CH2COO)3]·8H2O: a new example of a polyoxomolybdovanadate coordinated by a glycinato ligand

Abstract A new complex of formula K2[HMo6VIVVO22(NH3CH2COO)3]·8H2O has been prepared from molybdenum(VI) oxide and vanadium(V) oxide in aqueous solution by adding glycine and potassium chloride, and its structure determined by X-ray structure analysis. The molybdovanadate anion is built up of six MoO6 edge-sharing octahedra connected into a ring centered by a VO4 tetrahedron. The MoO6 octahedra are in pairs linked by the bridging glycine-carboxylato ligands.

Synthesis, structure and properties of molybdenum(VI) oxalate complexes of the types M2[Mo2O5(C2O4)2(H2O)2] and M2[MoO3(C2O4)] (M=Na, K, Rb, Cs)

The reaction of molybdenum(VI) oxide with oxalic acid or alkali oxalate and alkali halides results in the formation of two series of molybdenum(VI) oxalate complexes: one of the general formula M-2[Mo2O5(C2O4)(2)(H2O)(2)] containing the Mo2O5 core and the other of the formula M-2[MoO3(C2O4)] with a MoO3 core (M = Na, K, Rb, Cs). Both series were characterized by chemical analysis, ESR, UV and IR spectroscopy, thermogravimetry, differential scanning calorimetry, X-ray powder method and some of them by single-crystal X-ray structure analysis. Complexes of the first series adopt dimeric structures, the second series infinite polymeric structures. In both types of structures molybdenum ions are six-coordinated being surrounded by terminal ore-oxygens, bridging oxygens and bidentate bonded oxalate ligands. When exposed to UV light all these complexes in the solid state exhibit photochromic behavior changing color from colorless to green-brown. These changes are remarkably more pronounced in the complexes with dimeric structures. There is definite correlation between their coloration and the UV induced ESR signal indicative for molybdenum(V). Such behavior is explained by the partial reduction of Mo(VI) to Mo(V) only at the crystal surfaces. This is also the explanation why K-2[Mo2O5(C2O4)(2)(H2O)(2)] was so far described as being red or pale reddish tan. All attempts to prepare the corresponding lithium complexes were unsuccessful. They are most probably very unstable because of the small radius of the lithium ion

New Dinuclear Molybdenum(V) Complexes With β′‐Hydroxy‐β‐enaminones Containing a 4‐Hydroxy‐2‐pyrone Ring

New dinuclear molybdenum(V) complexes of the general formula [Mo2O4L2D2], were prepared by the reaction of [Mo2O3(acac)4] (acac = acetylacetonate ion) with β′-hydroxy-β-enaminones (L). All prepared complexes consist of Mo2O42+ cores coordinated by two ligands L via two donor oxygen atoms as in the analogous β-diketonates. The usual octahedral coordination around the molybdenum atoms is completed by the monodentate solvent molecules D (methanol, ethanol, or 2-propanol). All compounds were characterized by elemental analyses, IR, one- and two-dimensional NMR spectra, and thermal analysis, and some of them by X-ray crystallography (1a, 4a, 8b, and 9a). (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

Synthesis and structure of [(CH3)4N]4[H2MoV9O28]Cl·6H2O

Abstract [(CH 3 ) 4 N] 4 [H 2 MoV 9 O 28 ]Cl·6H 2 O has been synthesized from ammonium vanadate and molybdenum(VI) oxide in acidic aqueous solution by adding tetramethylammonium chloride, and its structure determined by single-crystal X-ray analysis. The polyoxomolybdovanadate anion has the structure of the decavanadate anion with the molybdenum atom substituted at one “capping” vanadium site. Owing to the 2/ m symmetry of the anion, this molybdenum atom is randomly distributed over four “capping” metal atom positions. Two hydrogen atoms are bonded to triply bridging oxygen atoms.

Synthesis, structure and ESR spectrum of (Hmorph)6[VIV, VV, Mo10)VO40] · 3H2O

Abstract The title compound has been synthesized from molybdenum(VI) oxide and ammonium vanadate in aqueous solution by adding morpholine (pH 5.8). The X-ray structural investigation shows that the polyoxometalate anion adopts a Keggin-type structure with a central tetrahedral vanadium(V) atom. The other two vanadium atoms are crystallographically disordered over 12MO 6 octahedral sites. The ESR spectrum clearly indicates that one octahedrally coordinated vanadium atom has the oxidation number +4.

Synthesis and structure of [Mo2O4(acac)2thala]·3C2H5OH with thala=3-(2-thienyl)-dl-alanine as a third bridging ligand between two molybdenum atoms

Abstract As part of our study on oxomolybdenum(V) complexes we present here the synthesis and crystal structure of a novel dimeric oxomolybdate(V) [Mo2O4(acac)2thala]·3C2H5OH (acac=acetylacetonato, thala=3-(2-thienyl)- dl -alanine) in which two molybdenum atoms are being bridged not only by two oxo-oxygens but additionally by the amino acid carboxylate group. Two octahedrally coordinated molybdenum atoms are singly bonded to each other at a distance of 2.5631(5) A.

Molybdenum(V) complexes with monothio-β-diketones: thiodipivaloylmethane, thiodibenzoylmethane and benzoylthioacetone

The preparations of oxomolybdenum(V) complexes with thiodipivaloylmethane (Htdpm), [Mo2O3(tdpm)4]1 and [But2C3HS2][MoO(SH)3(tdpm)]2, thiodibenzoylmethane (Htdbm), [Mo2O3(tdpm)4]3, and both benzoylacetone (Hba) and benzoylthioacetone (Hbta), [Mo2O3(ba)3(bta)]4, are described. Crystal structures of 1 and 2 have been determined by X-ray diffraction techniques. Complex 1 is dinuclear, the anion of 2 mononuclear, both containing the molybdenum atoms in distorted-octahedral geometry. The charge transfer between the cation and anion of 2 is associated with close contacts between both the dithiolylium sulfurs and the SH-sulfur atom S(3)[S ⋯ S 3.335(2) and 3.515(2)A].

Synthesis, structure and ESR spectrum of the triclinic and monoclinic forms of hydrated K8[Mo8(VIV)V4O40]

Abstract The triclinic K 8 [Mo 8 (V IV )V 4 O 40 ]·10H 2 O ( I ) and monoclinic K 8 [Mo 8 (V IV ) V 4 O 40 ]·9 2 O ( II ) have been prepared from molybdenum(VI)-oxide and ammonium vanadate in aqueous solution by adding potassium hydroxide and their structures characterized by ESR spectra and X-ray structure analysis. The structure of the same [Mo 8 (V IV )V 4 O 40 ] 8− anion in both compounds is based on a central VO 4 tetrahedron surrounded by a puckered ring of eight edge-sharing MoO 6 octahedra, with four VO 4 tetrahedra filling the gaps between the pairs of octahedra. The ESR spectra of both compounds clearly indicate that one vanadium atom is in the +4 oxidation state. In the crystal structurek molybdovanadate anions are interconnected by K + ions and water molecules.

Ba3[V10O28].19H2O

The crystal structure of barium decavanadate nonadecahydrate, Ba3[V10O28].19H2O, has been determined. The polyanion consists of ten distorted VO6 edge-sharing octahedra, with well established structure. There are two crystallographically independent decavanadate anions in the asymmetric unit, located around the centres of inversion at ½, 0, 0 and 0, ½, ½. Each of the three Ba2+ cations is surrounded by nine O atoms from water molecules and [V10O28]6− anions in a distorted square antiprism with one additional vertex.