Radical or Not Radical: Compared Structures of Metal
(M = Ni, Au) Bis-Dithiolene Complexes with a Thiazole Backbone
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Abstract
A complete series of dianionic, monoanionic,
and neutral dithiolene complexes formulated as [Ni(Et-thiazdt)<sub>2</sub>]<sup><i>n</i></sup>, with <i>n</i> =
−2, −1, 0, and Et-thiazdt: <i>N</i>-ethyl-1,3-thiazoline-2-thione-4,5-dithiolate,
is prepared using an optimized procedure described earlier for the
N–Me derivatives. Electrochemical and spectroscopic properties
confirm the electron-rich character of the Et-thiazdt dithiolate ligand.
The three complexes are structurally characterized by single-crystal
X-ray diffraction. The paramagnetic anionic complex [Ni(Et-thiazdt)<sub>2</sub>]<sup>−1</sup>, as Ph<sub>4</sub>P<sup>+</sup> salt,
exhibits side-by-side lateral interactions leading to a Heisenberg
spin chain behavior. The solid-state structure of the neutral, diamagnetic
[Ni(Et-thiazdt)<sub>2</sub>]<sup>0</sup> complex shows a face-to-face
organization with a large longitudinal shift, at variance with the
structure of its radical and neutral gold dithiolene analogue described
earlier and formulated as [Au(Et-thiazdt)<sub>2</sub>]<sup>•</sup>. Comparison of the two structures, and those of the other few structurally
characterized pairs of Ni/Au dithiolene complexes, demonstrates the
important role played by overlap interactions between gold dithiolene
radical species. Despite its closed-shell character, the neutral nickel
complex [Ni(Et-thiazdt)<sub>2</sub>]<sup>0</sup> exhibits a semiconducting
behavior with a room-temperature conductivity σ<sub>RT</sub> ≈ 0.014 S cm<sup>–1</sup>