Divalent metal complexes (Ca, Sr, Ba, Yb) of the unsymmetrical 3-(2′-thienyl)-5-(trifluoromethyl)pyrazolate ligand

The divalent complexes [M(ttfpz)(2)(thf)(4)] (ttfpz = 3-(2'-thienyl)-5-(trifluoromethyl)pyrazolate; M = Yb, 1, Ca, 2, Sr, 3, Ba, 4; thf = tetrahydrofuran)and [M(ttfpz)(2)(dme)(n)] (M = Ca, 5, Sr, 6, Yb, 7, n = 2; M = Ba, 8, n = 3; dme = 1,2-dimethoxyethane)have been prepared by redox transmetallation/protolysis reactions employing the free metals, Hg(C6F5)(2) and ttfpzH in donor solvents and their structures determined. The monomeric structures exhibit eta(2)-bound pyrazolate ligands with eight-coordinate metal atoms for complexes 1-7 and a ten-coordinate metal for 8. The pyrazolate ligands in the thf-complexes 1-4 as well as dme-derivatives 5 and 6 are in a transoid configuration, whilst in complex 7 the ttfpz ligands exhibit a cisoid relationship. In 8 the ligands have an intermediate role in between cisoid and transoid.