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 ] · n solv, 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 ] · n solv, 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 , η 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 η 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 η 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.