Molybdenum chalcogenide halides

Metal-Metal Bonds in Molybdenum Chalcogenide Halides... 

VII. Molybdenum A recent review of molybdenum chalcogenide halides is contained in a paper of Tsigdinos (432). 

Just as, in Group VB, niobium, so, in this Group, molybdenum provides most of the examples of the chalcogenide halides. The occurrence and preparation of such compounds are described in numerous publications. In most cases, they have been obtained as powders, with the composition based on chemical analyses only. The presence of defined, homogeneous phases is, therefore, in many cases doubtful. In addition, some published results are contradictory. A decision is possible where a complete structure analysis has been made. As will be shown later, the formation of metal-metal bonds (so-called clusters), as in the case of niobium, is the most characteristic building-principle. Such clusters... 

The most important binary systems which (formally) involve MoIV are the chalcogenides MoS2 and MoSe some comments on these systems are included in Section 36.6.3. The synthesis and properties of molybdenum(IV) halides have been thoroughly investigated.1,60... 

Solid-state cluster chemistry is dominated by octahedral (M 5L8)L6 and (MsLi2)L units which are the focus of this paper. These two cluster types are different in the way the metal octahedral core is surrounded by the ligands. In (MsLg)L6-type clusters (Fig. 6.1a), typical for molybdenum and rhenium halides, chalcogenides, and chalcohalides, eight innei hgands (L ) cap the octahedron faces and six outer ligands (L ) are located in the apical positions [9]. For metals with a smaller number of valence electrons, the (M6L i2)L -type clusters... 

Apart from the oxides and sulphides, other groups of simple compounds are the halides, chalcogenides and molybdates, and there are a number of well characterised organic compounds. Simple halides can be prepared by direct reaction between molybdenum powder and chlorine, fluorine or bromine, and the pentachloride MoClg has been used as a chlorination catalyst. 

Fer] Ferro, R., Marassa, R., HI. Crystal Stracture and Density Data, III-l. Alloys and Compounds other than Halides and Chalcogenides in Molybdenum, Phys.-Chem. Properties of its Compounds and Alloys , Atomic Energy Rev., Spec. Issue N7 359-507 (1980) (Crys. Stracture, Review, 961)... 

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