A copper(II)-pyrazole complex cation with (macro)3 imposed symmetry.

The reaction of Cu(ClO(4))(2) x 6H(2)O, NaAsF(6) and excess pyrazole yields hexakis(pyrazole-kappa N(2))copper(II) bis(hexafluoroarsenate), [Cu(C(3)H(4)N(2))(6)](AsF(6))(2) or [Cu(pzH)(6)](AsF(6))(2) (pzH is pyrazole), (I). The analogous hexakis(pyrazole-kappa N(2))copper(II) hexafluorophosphate perchlorate complex, [Cu(C(3)H(4)N(2))(6)](PF(6))(1.29)(ClO(4))(0.71) or [Cu(pzH)(6)](PF(6))(1.29)(ClO(4))(0.71), (II), is obtained in a similar fashion, using KPF(6) in place of NaAsF(6). Both compounds contain the hitherto unknown [Cu(pzH)(6)](2+) complex cation, in which the copper(II) ion lies at the center of a regular octahedron of coordinated N atoms. The cation has crystallographically imposed -3 symmetry. The X-ray data indicate that the lack of the expected distortion can be accounted for by the presence of either static Jahn-Teller disorder or dynamic Jahn-Teller distortion.