PREPARATION AND THE COVALENT HYDRATION OF A HEXAFLUORO-2,4-PENTANEDIONATOTETRAAMINECOBALT(III) COMPLEX

Twelve title complexes are prepared as perchlorate salts. These are Co(hfac)L2+ with L=(MeNH2)4, (n-AmNH2)4, cis-(NH3)2(en), (R-pn)(S-pn), cyclen, cyclam, cis-(NH3)2(bpy), (en)(bpy), (en)(phen), (tn)(bpy), (tn)(phen) and (bpy)(phen) where Hhfac=hexafluoro-2,4-pentanedione, MeNH2=methylamine, n-AmNH2=n-amylamine, en=ethylenediamine, pn=propylenediamine, cyclen=1,4,7,10-tetraazacyclododecane cyclam=1,4,8,11-tetraazacyclo-tetradecane, bpy=2,2'-dipyridyl, phen=1,10-phenanthroline and tn=1,3-propanediamine. The thermodynamic covalent hydration equilibrium constants K(OH) in water and K(OMe) in methanol are estimated for these complexes and for previously obtained Co(hfac)L2+ by UV spectrophotometry. The values critically depend on the involvement as L ligand of a bpy or a phen ligand. pK(OH) almost-equal-to - 6.6 and pK(OMe) almost-equal-to - 8.7 when L involves neither bpy nor phen ligand. pK(OH) almost-equal-to - 8.7 and pK(OMe) almost-equal-to - 11.0 when L involves either a bpy or a phen ligand. pK(OH) almost-equal-to - 11.5 and pK(OMe) almost-equal-to - 14.6 when L involves two bpy or phen ligands. The isomeric structure of the complex is also discussed on the basis of the fluorine NMR spectra.