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

A complete series of dianionic, monoanionic, and neutral dithiolene complexes formulated as [Ni­(Et-thiazdt)2]n, with n = −2, −1, 0, and Et-thiazdt: N-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 σRT ≈ 0.014 S cm–1.

本研究采用此前针对N-甲基（N–Me）衍生物报道的优化合成方法，制备了一系列完整的二阴离子、单阴离子及中性二硫烯配合物（dithiolene complexes），其通式为[Ni(Et-thiazdt)₂]ⁿ（n = -2、-1、0），其中Et-thiazdt为N-乙基-1,3-噻唑啉-2-硫酮-4,5-二硫代配体（N-ethyl-1,3-thiazoline-2-thione-4,5-dithiolate）。电化学与光谱学性质表征证实，Et-thiazdt二硫代配体具备富电子特性。上述三种配合物均通过单晶X射线衍射（single-crystal X-ray diffraction）完成结构解析。以四苯基鏻（Ph₄P⁺）为抗衡阳离子的顺磁性单阴离子配合物[Ni(Et-thiazdt)₂]⁻，通过侧向平行相互作用呈现出海森堡自旋链（Heisenberg spin chain）行为。中性抗磁性配合物[Ni(Et-thiazdt)₂]⁰的固态结构呈现面对面堆积模式，且存在较大纵向位移，这与此前报道的自由基型中性金二硫烯类似物[Au(Et-thiazdt)₂]•的结构存在显著差异。通过对比这两种配合物的结构，以及其他少数已完成结构解析的Ni/Au二硫烯成对配合物，可明确金二硫烯自由基物种间的重叠相互作用发挥了关键作用。尽管该中性镍配合物[Ni(Et-thiazdt)₂]⁰具有闭壳层特性（closed-shell character），但其室温电导率（room-temperature conductivity）σRT≈0.014 S·cm⁻¹，展现出半导体行为（semiconducting behavior）。