Tungsten tetraiodide

Iodides. Tungsten tetraiodide [14055-84-6] WI, is a black powder that is decomposed by air. It is prepared by the action of concentrated hydriodic acid on tungsten hexachlotide at 100°C. 

It was originally separated from zirconium by repeated recrystallization of the double ammonium or potassium fluorides by von Hevesey and Jantzen. Metallic hafnium was first prepared by van Arkel and deBoer by passing the vapor of the tetraiodide over a heated tungsten filament. Almost all hafnium metal now produced is made by reducing the tetrachloride with magnesium or with sodium (Kroll Process). 

Titanium tetraiodide can be prepared by direct combination of the elements at 150—200°C it can be made by reaction of gaseous hydrogen iodide with a solution of titanium tetrachloride in a suitable solvent and it can be purified by vacuum sublimation at 200°C. In the van Arkel method for the preparation of pure titanium metal, the sublimed tetraiodide is decomposed on a tungsten or titanium filament held at ca 1300°C (152). There are frequent hterature references to its use as a catalyst, eg, for the production of ethylene glycol from acetylene (153). 

High purity zirconium was first produced by van Arkel and de Boer in 1925. They vaporized zirconium tetraiodide [13986-26-0] into a bulb containing a hot tungsten filament which caused the tetraiodide to dissociate, depositing zirconium on the filament. 

By ring forming reactions /rans-Bromotetracarbonyl(methyl-methylidyne)tungsten, 49 Calcium acetate, 60 Chromium carbene complexes, 82 Ethyl (Z)-3-bromoacrylate, 130 Methyllithium, 188 By ether cleavage Diphosphorus tetraiodide, 127 Other methods... 

In addition to the tungsten(II) bonde mentioned above, the element forms at least two other borides, W2B and WB2 it forms a similar series of phosphides, W2P, WP, and WP2 as well as W02 (brown oxide), W4On (blue oxide), and WO3 (yellow oxide), and two sulfides, WS2 and WS3. The tungsleu(IV) oxide and sulfide are representative uf the simple Lelravalent compounds, which also include a tetrabromide, WBr4, and tetraiodide, WI4. Like lire drhalides, these tetiahalides undergo hydrolysis quite readily. 

In 1925 van Arkel and de Boer [19.2] published their first report about their famous method of producing metals in pure form by thermal decomposition of the metal iodide. In the zirconium case, impure zirconium metal is placed in an evacuated container and treated at 300°C with iodine vapor to form Zrl,. This tetraiodide is diffused to an electrically heated filament of tungsten or zirconium wire. At 1300-1400°C the zirconium iodide is dissociated to iodine gas and very ductile zirconium metal. From 1925 to 1945 the iodide process was the method used for obtaining pure, ductile zirconium metal. 

The reductive coupling of carbonyl compounds to olefins has also been effected by WCl6-LiAlH4, and by some tungsten and molybdenum carbonyls/ Further procedures for the deoxygenation of epoxides to olefins are described/ trifluoroacetyl iodide with sodium iodide and diphosphorus tetraiodide are particularly effective and can be used under mild conditions. 

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