Trivalent rare earth complexes of the unsymmetrical 3-(2 '-thienyl)-5-(trifluoromethyl)pyrazolate ligand

Trivalent rare earth complexes of the unsymmetrical 3-(2 -thienyl)-5-(trifluoromethyl)pyrazolate (ttfpz) ligand, namely [RE(ttfpz)(3)(thf)(3)]center dot nsolv, where thf = tetrahydrofuran [RE = La, solv = PhMe, n = 0.5 (1); RE = Sm, n = 0 (2); RE = Tb, solv = thf, n = 1 (3)], [RE(ttfpz)(3)(thf)(2)] [RE = Y (4), Ho (5), Lu (6), Sc (7)] and [RE(ttfpz)(3)(dme)(2)]center dot nsolv, where dme = 1,2-dimethoxyethane [RE = La, n = 0 (8a); RE = La, solv = Et(2)O, n = 0.5 (8b); RE = Eu, solv = dme, n = 1 (9)], were prepared, mainly by redox transmetallation/protolysis from the free metal, Hg(C(6)F(5))(2) and ttfpzH, and structurally characterised. In the nine-coordinate, pseudo-octahedral complexes 1 and 2, eta(2)-pyrazolate and thf ligands are in a facial arrangement, whereas they are arranged meridionally in 3. In the eight-coordinate complexes 4-7 the arrangement of the eta(2)-pyrazolate and thf ligands can be described as in between pseudo-trigonal bipyramidal and -square pyramidal. Ten-coordinate complexes 8a, 8b and 9 exhibit eta(2)-bonded pyrazolates and two chelating dme ligands as opposed to the nine-coordinate 3,5-diphenylpyrazolate (Ph(2)pz) complexes [RE(Ph(2)pz)(3)(dme)(2)], which possess one unidentate and one chelating dme ligand, suggesting that the ttfpz ligand is less bulky than Ph(2)pz