Co-ordination of copper(II) ions doped in pentacyanonitrosylferrate(2–) and tetrathiocyanatometallate(II) salts: an electron spin resonance study

Abstract

Pentacyanonitrosylferrate(2–) salts, M[Fe(CN)₅NO](M = Cd or Zn), doped with low concentrations of copper(II) ions give e.s.r. spectra characteristic of square-planar copper with the unpaired electron in the d_x²–y² level on copper and strongly interacting with four equivalent nitrogen atoms. The g- and A(⁶³Cu)-tensor components provide evidence for extensive in-plane π bonding. Similarly, metal tetrathiocyanates, M¹[M²(SCN)₄](M¹, M²= Zn, Cd, or Hg), doped with Cu^II ions give complexes having a distorted square-planar geometry (again d_x²–y² for the outer electron), with strong hyperfine coupling to four equivalent nitrogen atoms for Cu²⁺ in Zn[Hg(SCN)₄], two equivalent nitrogen atoms in Cd[Cd(SCN)₄], and none in the Zn[Cd(SCN)₄]. These results are discussed in terms of the co-ordinating power of the thiocyanate ligands.