Odd–Even Effect Observed in [Ni(dmit)2] Complex Salts of Quaternary Ammonium Cation with Both Benzyl Groups and ω-Phenylalkyl Groups

Abstract

Abstract A series of [Ni(dmit)2] (dmit: 1,3-dithiole-2-thione-4,5-dithiolate) complex salts of benzyldimethyl(ω-phenylalkyl)ammonium cation (BnCnPh: n represents the alkylene chain length; n = 1–4) have been prepared and characterized by X-ray crystallographic structural analysis. All complex salts were found to be composed of alternant stacks of layers of [Ni(dmit)2] anion dimers and cations (Layer I), and isolated cation layers (Layer II). In BnC3Ph complex salt, polymorphs, P<span style="text-decoration: overline;">1</span> (α-form) and P2(1)/c (β-form) crystals are obtained from similar crystallizing conditions. One of the biggest structural differences is the arrangement of [Ni(dmit)2] anion dimers; herringbone in α-form, while nearly parallel in β-form. Other BnCnPh complex salts adopt herringbone structure. Interestingly, BnCnPh series (n = 1, 2, 3α, 4) exhibit three types of pronounced odd–even effect in the crystal structures; 1. Dihedral angles between the two kinds of terminal phenyl groups, 2. Angles between [Ni(dmit)2] anion dimers, and 3. Ni–N+ distances. Such a structural feature is a consequence of the bulkiness of cation involving two phenyl groups. Introduction of terminal phenyl group is concluded to have increased the steric effect and led to the formation of the novel crystal structure of [Ni(dmit)2] complex salts.