STRUCTURE, SPECTROSCOPIC AND ANGULAR-OVERLAP STUDIES OF TRIS(PYRAZOL-1-YL)METHANE COMPLEXES

The metal(II) complexes [M{(pz)3CH)2][NO3]2, where (pz)3CH is the symmetrical tripodal nitrogen-donor ligand tris(pyrazol-1-yl)methane, have been prepared for M = Co, Ni, Cu or Zn, and examined by single-crystal X-ray diffraction and electronic spectroscopy. The cations are centrosymmetric with the copper complex exhibiting a Jahn-Teller distortion. The ligand 'bite' angles N-M-N of 83.3(9)-86.2(1)-degrees cause a slight trigonal distortion from octahedral geometry. The tripod ligand produces a relatively strong ligand field, consistent with the rather short metal-nitrogen bond lengths in the complexes. The pyrazole group acts as a moderately strong sigma donor and a weak out-of-plane pi donor, with the pi interaction in the plane of the amine ligand probably being close to zero.