PERFLUOROPHENYLANTIMONY ACETATES(I) - SYNTHETIC AND SPECTROSCOPIC STUDIES (UV, IR, H-1 AND F-19 NMR) OF SOME NEW TRIS(PENTAFLUOROPHENYL)ANTIMONY(V) DIACETATES

A series of new tris(pentafluorophenyl)antimony(V) diacetates of the type (C6F5)3Sb(OCOCH3-nRn)2 (R=Cl, F; n=0-3: R=-OC6H5, -OC6H4Cl-4, -OC6H3Cl2-2,4, -OC6H2Cl3-2,4,5; n=1) have been synthesized by the reaction of tris(pentafluorophenyl)antimony(V) dichloride and a carboxylic acid in the presence of triethylamine or the sodium/potassium salt of the carboxylic acid in the presence of 15-crown-5 or 18-crown-6 as a phase-transfer catalyst. A representative alkyl derivative, viz. trimethylantimony(V) diphenoxyacetate, was also synthesised by similar methods for spectral comparisons. The synthesis of tris(pentafluorophenyl)antimony(V) diacetate was also accomplished by reaction of tris(pentafluorophenyl)antimony(III) with acetic anhydride in the presence of equimolar quantities of periodic acid. These compounds were characterised by spectroscopic and elemental analyses as trigonal bipyramidal with the acetate ligand in all the derivatives behaving as a monodentate ligand. A correlation in the F-19 chemical shift and the pK(a) values of the acetates has been observed.