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

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 center dot center dot center dot O distances (2.46-2.52 angstrom), 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 center dot center dot center dot S intermolecular contacts [3.332(2) angstrom], leading to a pairing of the radical [Ni(S2O4)(2)](-) into antiferromagnetic uniform spin chains.