SYNTHESIS, VIBRATIONAL SPECTROSCOPY AND EXAFS ANALYSIS OF SOME DIVALENT AND TRIVALENT TRIFLUOROMETHANESULPHONATO COMPLEXES

The syntheses of trifluoromethanesulphonato (OTf) complexes of Co(II), Ni(II), Cu(II), Fe(III) and Ga(III) by the reaction of simple metal salts (Cl-, Br-, CO32-, ClO4-) or metallic gallium with trifluoromethanesulphonic acid have been systematically investigated. Comparison of the vibrational spectra of coordinated OTf in these complexes with that in simple ionic salts indicates the ligand to be bridging bidentate in M(OTf)3, M = Ga, Fe and in M(OTf)2, M = Cu and bridging tridentate in M'(OTf)2, M' = Co, Ni, Cd. EXAFS spectroscopic data can be interpreted in terms of layered structural arrangements for Co, Ni, Cd and Ga trifluoromethanesulphonato complexes, similar to that of the corresponding anhydrous metal perchlorates studied previously. In Cu(OTf)2, however, the copper atom is in a square planar environment. The short metal-oxygen distances, 1.96-2.09 angstrom are consistent with strong interactions between the ligand and metallic centre.