Isomorphous series of heterometallic complexes Na4[CuxCo(1-x){N(CH2PO3)3}]•13H2O and Na4[CuxZn(1-x){N(CH2PO3)3}]•13H2O (x=1...0): Synthesis and structural characterization by analysis of 3d-metal coordination polyhedra as compared with isodimorphous series Na4[CuxNi(1-x){N(CH2PO3)3}]•nH2O

The symmetry of the coordination environment of 3d metal atoms in mixed nitrilo-tris(methylenephosphonate) complexes CuxZn(1-x), CuxNi(1-x) and CuxCo(1-x) (x = 1...0) has been studied using the method for quantitative estimation of the degree of similarity of coordination polyhedra (CP) to regular polyhedra. The degree of similarity Phi and the degree of invariance of the electron density eta have been proposed and successfully used to estimate the coordination geometry of the analyzed complexes. For mixed Cu-Co-NTP and Cu-Zn-NTP complexes, the degree of similarity of CP to a regular trigonal bipyramid (TBP) has a smooth maximum attributing to changing the CP distortion character. It changes from the distortion characteristic of individual Co- and Zn-based complexes and revealed as longer M-N bond to the distortion characteristic of individual Cu-based complex manifested as lengthening of one of the M-O bonds. In the Cu-Ni-NTP isodimorphous series, the degree of similarity of CP to each of the regular polyhedra used for considering the individual phases (octahedron and TBP for Ni- and Cu-based complexes, respectively) increases with approaching the transition point and has a sharp maximum at this point. (C) 2020 Elsevier Ltd. All rights reserved.