Trimethylsilyl perrhenate

Submitted bt Max Schmidt and Hubebt Schmidbaub Checked by Shebman Thomas f and Dotie BBiTTONf 

Elementary rhenium in the form of a fine metal powder undergoes complete combustion in a stream of dry oxygen, quantitative yields of rhenium(VII) oxide being formed. Rhenium (VII) oxide is very sensitive to moisture and should be handled under anhydrous conditions, e.g., in a good dry-box. The compound is commercially available also.J 

One and twenty-two hundredths grams (0.0025 mol) of rhenium(VII) oxide is added to 12.5 ml. of hexamethyl-disiloxane, which has been dried and distilled over sodium wire in a 100-ml. round-bottomed flask. The reaction flask is fitted with a reflux condenser protected from laboratory air by means of a drying tube. The reaction mixture is refluxed and stirred (magnetically) until all the rhenium-(VII) oxide has disappeared and a clear colorless solution 

Rhenium metal powder is oxidized quantitatively to perrhenic acid by dissolution in 6 M nitric acid followed by repeated evaporation with concentrated nitric acid nearly to dryness. On dilution with 25 ml. of water, neutralization with 6 M sodium hydroxide, and the addition of slightly more than the stoichiometric amount of silver nitrate dissolved in as little water as possible, silver perrhe-nate precipitates in the form of colorless crystals. These additions are made in a beaker protected from light. The solution is decanted from the product, which is dried in an oven at 110° for 8 hours. 

One and thirty-five hundredths grams of silver perrhenate is added, with stirring, to 10 ml. of dry hexamethyldisiloxane in a 100-ml. round-bottomed flask. One milliliter of tri-methylchlorosilane is added. The mixture is stirred for 

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See also Cycloheptatrienemolybdenum(O) tricarbonyl, synthesis 31 Trimethylsilyl perrhenate, synthesis 39... 

Trimethylsilyl perrhenate forms colorless crystals, which are very sensitive to hydrolysis and which must be handled in a dry atmosphere. Under anhydrous conditions, the compound is stable to light and oxidation. Contaminated products undergo slow decomposition at room temperature, blue reduction products of Re(VII) being formed. In an excess of water trimethylsilyl perrhenate is hydrolyzed quickly and quantitatively. The perrhenic acid formed in this reaction together with trimethylsilanol can be determined by acidimetric titration or precipitation as nitron perrhenate. Trimethylsilyl perrhenate is soluble without decomposition in all common anhydrous and aprotic solvents (benzene, cyclohexane, ethyl ether, tetrahydro-furan, chloroform, etc.). 

CgHgNgSi, Trimethylazidosilane (gas-ed), 38B, 1068 CgHgORbSi, Rubidium trimethylsilanolate, 35B, 440 CgHgOgSig, HexamethyIcyclotrisiloxane, 18, 682 CgHgOftReSi, Trimethylsilyl perrhenate, 34B, 364 CgHioSi, Ethylmethylsilane (gas-mw), 38B, 1069 C3HioSi, Trimethylsilane (gas-ed), 18, 681... 

Trimethylsilyl perrhenate is also formed in the reaction of dichlorodimethylsilane with silver perrhenate in hexamethyldisi-loxane through a transesterification (yield 70%). The reaction and work-up follow the same procedures as described for Route 1 above ... 

Trimethylsilyl perrhenate and its germanium and tin analogs are synthons for the preparation of covalent and ionic perrhenates in dry nonpolar solvents, and sources for various organorhenium catalysts. 

The Beckmann rearrangement of cyclohexanone oximes produces caprolactams in high yield if the reaction is carried out in the presence of tetrabutylammonium perrhenate <93CL489>, and enaminolactams are obtained by the photolytic rearrangement of a,jS-unsaturated ketone oximes <88JCS(Pl)32l>. The treatment of acylated or sulfonylated oximes with trimethylsilyl iodide or... 

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