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Structural, Spectroscopic and Angular-overlap Studies of the Nature of Metal-Ligand Bonding for Tripod Ligands

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Astley, T and Canty, AJ and Hitchman, MA and Rowbottom, GL and Skelton, BW and White, AH (1991) Structural, Spectroscopic and Angular-overlap Studies of the Nature of Metal-Ligand Bonding for Tripod Ligands. Journal of the Chemical Society, Dalton Transactions, 8. pp. 1981-1990. ISSN 1477-9226

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Abstract

The metal(II) complexes [M((pz)2(py)CH}2][NO3]2 (M = Fe, Co, Ni, Cu or Zn), where (pz)2(py)CH is the unsymmetrical tripodal nitrogen-donor ligand bis(pyrazo1-1-yl)(pyridin-2-yl)methane, have been prepared and examined by single-crystal X-ray diffraction and single-crystal electronic spectroscopy. The structural studies, and the application of the angular overlap model to the spectroscopic results, provide new information on the bonding characteristics of tripod ligands and a comparison of pyrazole and pyridine groups. The zinc complex crystallizes in both the monoclinic(P21/c) and triclinic (P1 bar) systems, the monoclinic complex being isomorphous with those of cobalt and copper. The cations are centrosymmetric, but exhibit disorder in the orientation of the pyrazole and pyridine rings, except for the copper complex which exhibits a Jahn-Teller distortion involving two Cu-N(pz) bonds which are ca. 0.038 A longer than the other Cu-N distances. Except for the copper complex, the ligands form 'bite' angles N-M-N of 83.8(2)-86.9(2), resulting in 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 pyridine group is a slightly stronger sigma donor than the pyrazole groups, with both amines acting as weak pi donors.

Item Type: Article
Journal or Publication Title: Journal of the Chemical Society, Dalton Transactions
Page Range: pp. 1981-1990
ISSN: 1477-9226
Identification Number - DOI: 10.1039/DT9910001981
Date Deposited: 13 Jan 2008 22:39
Last Modified: 18 Nov 2014 03:27
URI: http://eprints.utas.edu.au/id/eprint/2853
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