Synthesis of Terminal Bis(hydrosulfido) and Disulfido Complexes of Ni(II) from a Geometrically Frustrated Tetrahedral Ni(II) Chloride Complex.

Recent studies have highlighted how reactive sulfur species (RSS) can be regulated and transported by metal-sulfur coordination compounds. We report herein the reactivity of PhB(tBuIm)3NiCl (1) with RSS, including the hydrosulfide anion ([Bu4N][SH]) and a reduced tetrasulfide ([K18-C-6]2[S4]). The strongly donating tris(carbene) ligand in 1 is geometrically constrained to a tetrahedral geometry, and the energetically preferable square planar geometry is not achievable with the [PhB(tBuIm)3]- ligand. Upon reaction of 1 with [Bu4N][SH] and [K18-C-6]2[S4], the square planar complexes PhB(tBuIm)2(tBuImH)Ni(SH)2 (2) and PhB(tBuIm)2(tBuImH)Ni(η2-S2) (3) are formed, respectively, via the protonation of one carbene ligand donor atom. Mechanistic investigation suggest that protonation occurs either from decomposition of 1 during the reaction progress, reactions with advantageous [Bu4N]+/[K18-C-6]+ countercations or from the generation of transient unidentified RSS that facilitate proton transfer reactions.