Synthesis and reactivity of a tris(carbene) zinc chloride complex

Abstract

The [^PhB(^tBuIm)₃]¹⁻ ligand has gained increased attention since it was first reported in 2006 due to its ability to stabilize highly reactive first row transition metal complexes. In this work, we investigate the coordination chemistry of this ligand with redox-inert zinc to understand how a zinc metal center behaves in such a strong coordinating environment. The ^PhB(^tBuIm)₃ZnCl (1) complex can be formed via deprotonation of [^PhB(^tBuIm)₃][OTf]₂ followed by the addition of ZnCl₂. Salt metathesis reaction with nucleophilic n-BuLi yields the highly carbon-rich zinc coordination complex ^PhB(^tBuIm)₃ZnBu (2) with three carbene atom donors and one carbanion donor. In contrast, reaction of complex 1 with a less nucleophilic polysulfide reagent, [K.18-C-6]₂[S₄], leads to the formation of a tetrahedral zinc tetrasulfido complex via protonation of one carbene donor to form ^PhB(^tBuIm)₂(^tBuImH)Zn(κ²-S₄) (3).