Sulfur Oxygenation of [Ni(btdt) 2 ] 2– by Aerial Oxidation under Ambient Conditions – Syntheses, Crystal Structures, and Properties of [Bu 4 N] 2 [Ni(btdt) 2 ] and [Bu 4 N] 2 ­[Ni(btdtO 2 ) 2 ]·H 2 O ({btdt} 2– = 2,1,3‐Benzenethiadiazole‐5,6‐dithiolate)

Abstract

[Bu4N]2[Ni(btdt)2] (1) ({btdt}2– = 2,1,3-benzenethiadiazole-5,6-dithiolate) was synthesized by treating one equivalent of NiCl2·6H2O with two equivalents of H2btdt in MeOH in the presence of NaOH under nitrogen, and then obtaining a precipitate by adding tetrabutylammonium bromide. When the same reaction is carried out under ambient conditions, it yields the trans-disulfinate complex [Bu4N]2[Ni(btdtO2)2]·H2O (2) along with complex 1. Complex 1 crystallizes in the triclinic space group P, whereas complex 2 crystallizes in the monoclinic space group C2/c. The NiII ion, coordinated with four sulfur atoms present in complex 1, shows almost square-planar geometry, but trans-disulfinate complex 2 shows distorted square-planar geometry around the NiII ion with a nonplanar molecular structure. Oxygen atoms of the sulfinates are involved in C–H···O and O–H···O hydrogen-bonding interactions, which might be important factors for the nonplanarity of complex 2. Complex 1 undergoes a reversible oxidation (ΔE = 0.09 V) at E1/2 = +0.22 V vs. Ag/AgCl and an irreversible oxidation at +0.77 V, whereas complex 2 shows quasi-reversible oxidation at E1/2 = +0.50 V vs. Ag/AgCl in acetonitrile solution.