Cyanide initiated perfluoroorganylations with perfluoroorgano silicon compounds

Cyanophenylphosphanes, Ph2PCN or PhP(CN)2, do not react with Me3SiCF3 or Me3SiC6F5 in the absence of cyanide ions. Catalytic amounts of ionic cyanides such as [NEt4]CN, [18-crown-6-K]CN or NaCN initiate perfluoroorganylation reactions. The trifluoromethylphosphines, Ph2PCF3 and PhP(CF3)2, as well as the pentafluorophenylphosphines, Ph2PC6F5 and PhP(C6F5)2, are isolated in 60–75% yield. In dimethylformamide or acetone solutions, side reactions are observed while reactions in CH2Cl2 and acetonitrile proceed selectively. Me3SiCF3 addition to the carbonyl groups of dimethylformamide and acetone occurs on treatment of Me3SiCF3 solutions of these solvents with catalytic amounts of cyanide, cyanate or thiocyanate salts even at low temperature. The formation of the reactive silicate [Me3Si(CN)CF3]− in reactions with an excess of [18-crown-6-K]CN is proved by low temperature NMR investigations.