Co-ordination chemistry of higher oxidation states. Part 7. Nickel(III) and nickel(II)–nickel(IV) complexes of ethylenediamine and related ligands. A clarification

Abstract

The chlorination of Ni(en)₂Cl₂(en = ethylenediamine) in alcohol is shown to yield either the nickel(III) complex trans-[Ni(en)₂Cl₂]Cl or the mixed-valence class II compound [Ni^II(en)₂Ni^IV(en)₂Cl₂]Cl₄ depending upon the conditions, and the confusion in the literature over the nature of these materials is corrected. Data are reported for the related complexes [Ni^III(en)₂Br₂]Br, [Ni^III(pd)₂X₂]X, [Ni^II(pn)₂Ni^IV(pn)₂Cl₂]Cl₄[pd = H₂N(CH₂)₃NH₂, pn = H₂NCH₂CH(CH₃)NH₂; X = Cl or Br], [Ni^III(en)₂Cl₂]ClO₄, and [Ni^II(en)₂Ni^IV(en)₂Cl₂][ClO₄]₄. Attempts to isolate Ni^III or Ni^II–Ni^IV complexes with Me₂N(CH₂)₂NMe₂ or o-C₆H₄(NMe₂)₂ failed.