Cyanide tetraphenylarsonium

Tetraphenylarsonium tellurapentathionate reacted readily in acetonitrile with tetra-phenylphosphonium cyanide to produce tellurocyanate9. The tellurocyanate was not isolated. 

Tetraphenylarsonium benzyl(bromocyanato)tellumte(II) was prepared from benzyl tellurium cyanide and the arsonium bromide3 and also from tetraphenylarsonium tellurocya-nate and benzyl bromide4. 

The tetraphenylarsonium cation is useful in coordination chemistry because of its large size. Tetraphenylarsonium cyanate dihydrate was prepared byNor-buryand Sinhain 1968. The preparation involved precipitation of the cyanate from an aqueous solution, but the method suffers from the disadvantage of low yields. Tetraphenylarsonium cyanide has been prepared from methanol solution with fairly good yields, but the product is isolated as the monohydrate. The ion-exchange method developed for the tetraalkylammonium salts can be readily applied to the preparation of anhydrous tetraphenylarsonium cyanate and cyanide, thus eliminating many of the problems initially involved in the synthesis of these componds. 

Tetraphenylarsonium cyanide is a hygroscopic white solid which must be stored in a dry inert atmosphere. The compound undergoes slow decomposition upon standing but can be repurified by the above recrystallization procedure. The compound melts, with decomposition, at ca. 219° and exhibits an appreciable degree of solubility in ethanol, methanol, and acetonitrile. The infrared spectrum, taken as a Nujol mull, exhibits bands due to v(CN) at 2250 (w) and 2058 (w) cm , in addition to those absorptions attributed to the tetraphenylarsonium cation. ... 

The tellurocyanate ion is stabilized by bulky onium cations. The reactions of tellurium with tetraethylammonium cyanide in dimethylformamide or acetonitrile , with tetramethyl-ammonium cyanide in acetonitrile , with tetraphenylarsonium cyanide in acetonitrile , or with bis[triphenylphosphane]iminium cyanide in acetone produced onium tellurocyanates that were isolated by evaporation of the solvent. The dry salts are reported to be unaffected by oxygen . Moist air and wet solvents decompose the tellurocyanates with depostion of tellurium . 

Both trityl chloride and perchlorate furnish the same product ratio reaction with tetraphenylarsonium cyanide (139), indicating that the electrophile must be the same—trityl cation. The preponderance of nitrile over isonitrile (9 1) must mean that the cation is relatively soft. 

Tetraphenylarsonium salts of the hexaiodocomplexes (7) of thorium (IV) and uranium (IV), [Ph Asl MI, have also been obtained by crystallisation of the tetraiodide/methyl cyanide complexes with tetraphenylarsonium iodide in methyl cyanide solution in the absence of free iodine which, when present, precipitates as Ph4AsI. ... 

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