A bond-valence approach to the semicoordination of copper-oxygen and copper-nitrogen complexes

Bond valence as the function of inter-nuclear distance for Cu-O and Cu-N bo nds were estimated. Based on the developed bond-valence theory a mutual dep endence between the bond length in copper coordination sphere with chromoph ores CuO6, CuO5, CuN6 and CuN4O2 has been derived and compared with the exp erimental structural correlations. The discontinued transition from chemica l bonding to the nonbonding state in the direction of the elongated bond wa s estimated. The shortest bond lengths are dependent on the copper atom val ence. The supreme manifestation of coordination sphere plasticity is estima ted as semicoordination. The semicoordinative Cu-O and Cu-N bonds are 3.07 and 2.78 Angstrom long. (C) 1999 Elsevier Science Ltd. All rights reserved.