Chevrel phases preparation

Cu4Mo6Seg. The triclinic structure of these compounds has been described by McGuire et al. (2006). It contains nearly regular Mo6 clusters the Cu atoms fully occupy four sites between faces of two adjacent Mo6Se8 clusters. This compound is a member of a series of MexMogX8 Chevrel phases. Preparation and properties have been discussed. A Cu intercalation apparatus was built for... 

We have already referred to the Mo/Ru/S Chevrel phases and related catalysts which have long been under investigation for their oxygen reduction properties. Reeve et al. [19] evaluated the methanol tolerance, along with oxygen reduction activity, of a range of transition metal sulfide electrocatalysts, in a liquid-feed solid-polymer-electrolyte DMFC. The catalysts were prepared in high surface area by direct synthesis onto various surface-functionalized carbon blacks. The intrinsic... 

Synthesis of sulfo-selenide Chevrel phases Phases ofM Mo x xSex composition (M = Cr, Mn) were prepared by the reaction of stoichiometric mixtures of MoS2 and MoSe2 binary powders with Mo and Cr, or Mn, metallic powders (Mantjour-Billah and Chevrel 2004). The mixtures were pressed into pellets and then (inside an alumina crucible) sealed in evacuated silica tubes. After heating to 800°C and then to 1000°C for 24 hours, two further grinding and annealing (at 1000°C) treatments were performed. Powder X-ray diffraction methods were used to study the solid solutions, the trend of the lattice parameters, etc. 

The Chevrel phase CuMoeSs was prepared by a ceramic method. What would be suitable starting materials and what precaution would you have to take ... 

The incentive for synthesis of molecular cluster complexes with the cluster cores M6E8 (M = Cr, Mo, W E = S, Se, ) has been to solve some of the structural problems in the Chevrel phases (40) and to find solution chemistry to prepare chromium or tungsten Chevrels (28, 77). 

Chevrel phase compounds, AxMo6Ch8 (Ch = S, Se or Te), may also be considered as intercalation compounds. Mo6S8 can be prepared by acid-leaching copper from CuxMo6S8. 

The literature dealing with this subject is enormous, and the reader should consult the references cited rather than any attempt be made to cover the subject in this review. Given the interesting properties of Chevrel phases, a considerable effort has recently been made to prepare molecular complexes with M6Q8 cluster cores. These serve both as molecular models and (in the case of tungsten) molecular precursors of solid-state materials. 

One of the stimuli for studying these complexes is their close relationship to the well-known Chevrel phases MMo Yg (Y = S, Se or Te). Accordingly, a noteworthy recent development is the discovery of octahedral rhenium-selenide clusters. The phase Re SegClj has been prepared by the high temperature reaction ( BOOK) of ReQj with mixtures of Re and Se. An X-ray crystal structure has shown the presence of the [RcgScg] core possessing Re—Re distances of 2.6 2.67 A. The presence of two terminal Re—Cl bonds tram to one another) inhibits interlayer linkages. ... 

There are a number of materials which have been studied but the two favorite ternary superconductors are the so called Chevrel phases, named after R. Chevrel (Universite de Rennes, France) who first prepared the MMo Sg or MMo Seg compounds (Chevrel et al. 1971), and the RRh4B4 compounds. In the Chevrel phases, M can be any number of metals including the rare earth metals, and in the latter compound R represents the rare earths and thorium. In both instances Matthias and his co-workers were the first to report the existence of superconductivity in the Chevrel phases (Matthias et al. 1972) and in RRh4B4 (Matthias et al. 1977),... 

The condensation of octahedra via common vertices, edges or faces leads to cluster units of a type known since the end of the 1970 s. Among these are the metal-rich subhalides of the early transition metals [186-188] and the Chevrel phases. [179, 189-192] The preparation of [Co9Sen(PPh3)6] (46) (Fig. 3-66) made it clear that this structural principle could be extended to the more electron-rich transition metals. [164, 168] All faces of the C09 cluster in 46 are capped by either /ig-or / 4-Se ligands. The Co atoms of the basal faces (Col, Co4, Co9, C06, Co7,... 

Chevrel compounds of the general formula A MogSg with A = Cu, Pb, La etc. are difficult to prepare in very pure state by the ceramic procedure. A one-step reduction of a precursor sulphide has been found to yield these phases (Nanjundaswamy et al, 1987) ... 

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