Synthesis of heterobimetallic tungsten acetylacetonate/alkoxide complexes and their application as molecular precursors to metal tungstates

Abstract

A series of M 2 W 2 (O) 2 (acac) 2 (OMe) 10 [M = Co (1), Ni(2), Mg (3), Zn (4)] have been synthesised and structurally characterised by X-ray crystallography. All the compounds share common structural features which are identical to the analogous molybdenum species, with four edge-sharing octahedra situated in the same plane, and incorporating two  3-bridging and four  2-bridging methoxide groups. The divalent metal M and tungsten have both octahedral coordination environments with six oxygen atoms. The structure of Na[Zn(acac) 3 ] (6), a by-product of a failed synthesis of 4, is also reported, and is a linear polymer in which [Zn(acac) 3 ] anions use all six oxygen atoms to link sodium cations either side of the anion. Thermal decomposition of representative samples (1, 3) shows them to be single-source precursors for metal tungstates MWO 4. When the decomposition is carried out under an autogenerated pressure (RAPET) at 700 o C 1 forms CoWO 4 nanoparticles, along with WOx-filled carbon nanotubes and amorphous carbon, while 3 forms MgWO 4 nanoparticles and rods, though the latter lack a carbon shell and are much shorter in length.

Aerosols: A Sustainable Route to Functional Materials

“…Metal tungstate precursors have also been synthesised and shown to be a route towards metal tungstate thin films . Here the precursors [M 2 W 2 (O) 2 (acac) 2 (OMe) 10 ], where M=Co, Ni, Mg or Zn, were synthesised by reacting [Ni(acac) 2 ], [Mg(acac) 2 ], [Zn(acac) 2 ] or [Co(acac)(OMe) ] with [WO(OMe) 4 ].…”

“…Metal tungstate precursors have also been synthesised and shown to be ar oute towards metal tungstate thin films. [68] Here the precursors [M 2 W 2 (O) 2 (acac) 2 (OMe) 10 4 ]. Such as ynthetic route would eliminate the need to use halogenatedp recursors and also use readily availablea nd chemically stable precursorsw ithnon-toxicb y-products produced.…”

Precursor directed synthesis – “molecular” mechanisms in the Soft Chemistry approaches and their use for template-free synthesis of metal, metal oxide and metal chalcogenide nanoparticles and nanostructures

“…Thus ambient pressure MOCVD has recently been reported for the deposition of relatively thick ZnO 78 and copper metal 79 lms. The Reaction under Autogenous Pressure at Elevated Temperatures (RAPET) [80][81][82][83] is a gas phase process organized in a way quite different from both MOCVD and ALD but has in its mechanisms a hidden but distinct relationship to both. RAPET is carried out by quick evaporation of large amounts of a metalorganic precursor in a small high-pressure sustaining vessel.…”

“…An idea to introduce specic ligands decreasing the temperature of thermal decomposition in the deposition processes, 162 for example, by introduction of a hydride ligand in the precursor structure bearing branched alkoxide ligands such as t-butoxide, turned in reality unsuccessful: the reaction mechanisms are not really molecularthe emerging nuclei of oxide get reduced and initiate polymerization and carbonization of the organic ligands (compare RAPET). [80][81][82][83] Introduction of more thermally stable ligands requiring an increase in deposition temperatures and permitting to avoid carbonization turned out to be a much more fruitful approach. This approach has been pioneered and propagated by A.C. Jones et al who proposed to use alkoxide beta-diketonate complexes 163 and also amino alkoxide modied alkoxides.…”

Tungsten-Based Mesoporous Silicates W-MMM-E as Heterogeneous Catalysts for Liquid-Phase Oxidations with Aqueous H2O2

“…The same acac chelating ligand was successfully employed for stabilization of Nb precursors in the synthesis of Nb-MMM-E materials using the same EISA methodology [48]. The formation of oxo alkoxide/acac WO(OR) x (acac) y complexes by the interaction of W oxo alkoxides with acac was addressed in the literature [53,54]. All of these prompted us to use acac in the synthesis of W-MMM-E materials.…”