Rhenium pentachloride

Submitted by Loren C. Hurd and Eugene Brimm Checked by W. A. Tabbed and B. S. Hopkins  

Rhenium pentachloride is prepared by the direct combustion of metallic rhenium in dry chlorine.1 

Metallic rhenium, prepared by the reduction of either potassium perrhenate (see synthesis 60A) or ammonium perrhenate (see synthesis 60B), is placed in a previously ignited porcelain boat and inserted in a pyrex combustion tube of the type shown in Fig. 31. All air in the train is displaced with nitrogen that has been passed through alkaline pyrogallol A and sulfuric acid B. 

When the system is free from oxygen, all portions of the tube are flamed to drive out moisture. If any water remains, it will react with rhenium pentachloride to form oxychlorides. When the tube is dry, the nitrogen is cut off, and chlorine introduced. Commercial chlorine that has been dried by sulfuric acid C has been found satisfactory. 

The boat and its contents are heated either with a wing-top Bunsen burner or with a short electric furnace. If a burner is used, the tube should be protected with a wire gauze. Although combustion usually takes place rapidly at about 400°C., the temperature should be so regulated that the rhenium burns slowly in an excess of chlorine. The speed of oxidation varies with the purity and state of 

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The formation of a monomeric amidino complex has been reported for the reaction of rhenium pentachloride with di-isopropylcarbodiimid. A composition of [ReCl4(prop 2N2CCI)] was derived from elemental analysis, spectroscopic data and the crystal structure of the molybdenum analogue. " ... 

More recently the methyl analogue of Re2Clg was prepared from monomeric rhenium pentachloride, as well as from the rhenium benzoate dimer, Re2(02CC6H5)4Cl2, which has the quadruple bond already established (80). Addition of excess methyllithium to ReCls in diethyl ether at —78°C followed by low-temperature isolation of the resultant red crystals produced Li2Re2(CH3)8 2(C2H5)20 in a 16% yield. 

The yield of rhenium pentachloride is generally in the neighborhood of 80 per cent. 

Rhenium pentachloride reacts energetically with water. If exposed to air, it fumes and evolves chlorine and hydrogen chloride. 

Rhenium trichloride is prepared by the thermal decomposition of rhenium pentachloride in an atmosphere of nitrogen.1... 

A combustion tube of either Jena hard glass or Corning 172 is constructed similar in design to that used for the preparation of rhenium pentachloride (synthesis 62). The pentachloride is prepared in the manner previously described and sublimed into the bulb D. The chlorine is then turned off, and the train swept out with nitrogen. When all chlorine has been displaced, the pentachloride is... 

Rhenium pentachloride, 180 Rhenium sulfide, 177 Rhenium trichloride, 182 Rubidium, metallic, 79... 

Rhenium Pentachloride and Volatile Metal Chlorides by Direct Chlorination 41... 

RHENIUM PENTACHLORIDE AND VOLATILE METAL CHLORIDES BY DIRECT CHLORINATION USING A VERTICAL-TUBE REACTOR... 

Rhenium pentachloride is obtained as black crystals. The solid melts at 261° with decomposition. It fumes in air, evolving hydrogen chloride and chlorine. 

Previous preparations of Re3Cl9 have involved driving the rhenium halides horizontally along bulb trains.1 2 The present procedure is a considerable improvement on these, because it involves decomposition of refluxing rhenium pentachloride in the reaction bulb. Yields are very high and, using the method for the preparation of rhenium pentachloride given in Sec. 11, yields of over 90% from rhenium metal are possible. 

The apparatus (Fig. 1) is flamed dry in a stream of dry nitrogen and transferred with the stopcock closed to a glove bag, previously flushed out with dry nitrogen. Rhenium pentachloride, 5-10 g, is placed in the bulb and the tube is removed from the glove bag and clamped in a vertical position with a moderately fast stream of nitrogen flowing. 

The bulb is heated with a medium Bunsen flame until the rhenium pentachloride melts and is refluxing up the tube.t From time to time heating is stopped and Re3Cl9 formed in the tube is scraped back into the bulb. After about 4 hr, or when no more brown fumes are seen and only solid is observed in the bulb, the apparatus is allowed to cool. The bulb is sealed off and transferred to a glove bag and the dark-red crystalline solid is transferred to ampules. The product can be purified by grinding with a mortar and pestle under nitrogen and pumping off any volatile rhenium halide oxides under vacuum. 

Rhenium pentachloride reacts with diisopropylcarbodiimide in CC14 to form the monomeric six-coordinate amidino complex ReCl4[Pr NC(Cl)NPri].623... 

Shortly after rhenium was discovered, rhenivim trichloride was prepared by thermal decomposition of rhenium pentachloride (172, 205). Reaction of rhenium trichloride with cesium chloride in hydrochloric acid produced a dark red salt of stoichiometry CsReCli ... 

Obtained (by-product) by Fries rearrangement of 2-tert-butylphenyl propionate in nitr-omethane at 20° with antimony pentachloride (7%) [6570,7561,7576] ot rhenium pentachloride (7%) in the same conditions [7576]. 

It should be borne in mind that the polymer structures shown above are simplistic since there are often many stereochemical forms of the repeat units. In certain cases highly stereoregular polymers can be formed, e.g. polymerization of racemic 1-methylnorbornene by rhenium pentachloride gives a polymer with a head-to-tail cw-syndiotactic microstructure Me Me... 

These reactions are catalyzed by systems similar to the Ziegler—Natta contacts, in particular, those containing tungsten hexachlorides, molybdenum and rhenium pentachlorides in the presence of alkylaluminum chlorides. 

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