Radical or Not Radical: Compared Structures of Metal (M = Ni, Au) Bis-Dithiolene Complexes with a Thiazole Backbone

Abstract

A complete series of dianionic, monoanionic, and neutral dithiolene complexes formulated as [Ni­(Et-thiazdt)₂]^<i>n</i>, 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)₂]⁻¹, as Ph₄P⁺ 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)₂]⁰ 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)₂]^•. 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)₂]⁰ exhibits a semiconducting behavior with a room-temperature conductivity σ_RT ≈ 0.014 S cm^–1