Dithiolene complexes as metallo-ligands: a crown-ether approach

Abstract

A nickel dithiolene complex substituted with crown ether cyclic moieties incorporating four O atoms, abbreviated as [Ni(S₂O₄)₂]^1−,0, is isolated in its radical anionic (as Na⁺ salt) and neutral forms. The Na⁺ cation is six-coordinated with short Na⋯O distances (2.46–2.52 Å), involving two crown ether moieties of two different complexes. The oxidized neutral complex [Ni(S₂O₄)₂]⁰ was also isolated and structurally characterized. In the absence of alkaline cations during the synthesis, a mixed salt associating [Ni(S₂O₄)₂]¹⁻ with Ni²⁺ was isolated, and formulated as (Ni,H₂O)[Ni(S₂O₄)₂]₂, with the Ni²⁺ cation weakly bonded to two crown ether moieties. The salt exhibits an unprecedented solid state association with extremely short S⋯S intermolecular contacts [3.332(2) Å], leading to a pairing of the radical [Ni(S₂O₄)₂]⁻ into antiferromagnetic uniform spin chains.