Trivalent Rare Earth Complexes of the Unsymmetrical 3-(2′-Thienyl)-5-(trifluoromethyl)pyrazolate Ligand

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Abstract

Trivalent rare earth complexes of the unsymmetrical 3-(2′-thienyl)-5-(trifluoromethyl)pyrazolate (ttfpz) ligand, namely [RE(ttfpz)3(thf)3]·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]·nsolv, where dme = 1,2-dimethoxyethane [RE = La, n = 0 (8a); RE = La, solv = Et2O, n = 0.5 (8b); RE = Eu, solv = dme, n = 1 (9)], were prepared, mainly by redox transmetallation/protolysis from the free metal, Hg(C6F5)2 and ttfpzH, and structurally characterised. In the nine-coordinate, pseudo-octahedral complexes 1 and 2, η2-pyrazolate and thf ligands are in a facial arrangement, whereas they are arranged meridionally in 3. In the eight-coordinate complexes 47 the arrangement of the η2-pyrazolate and thf ligands can be described as in between pseudo-trigonal bipyramidal and -square pyramidal. Ten-coordinate complexes 8a, 8b and 9 exhibit η2-bonded pyrazolates and two chelating dme ligands as opposed to the nine-coordinate 3,5-diphenylpyrazolate (Ph2pz) complexes [RE(Ph2pz)3(dme)2], which possess one unidentate and one chelating dme ligand, suggesting that the ttfpz ligand is less bulky than Ph2pz.

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