Static and dynamic Jahn-Teller distortions in CuN6 complexes. Crystal structures and EPR spectra of complexes between copper(II) and rigid, tridentate cis,cis-1,3,5-triaminocyclohexane (tach: Cu(tach)2(ClO4)2, Cu(tach)2(NO3)2. Crystal structure of Ni(tach)2(NO3)2