Structure, spectroscopic and angular-overlap studies of tris(pyrazol-1-yl)methane complexes

Abstract

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)° 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 σ donor and a weak out-of-plane π donor, with the π interaction in the plane of the amine ligand probably being close to zero.