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

Abstract

AbstractTrivalent 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 4–7 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.