Tris(2-mercaptoimidazolyl)hydroborato Cadmium Thiolate Complexes, [TmBut]CdSAr: Thiolate Exchange at Cadmium in a Sulfur-Rich Coordination Environment

A series of cadmium thiolate compounds that feature a sulfur-rich coordination environment, namely [TmBut]CdSAr, have been synthesized by the reactions of [TmBut]CdMe with ArSH (Ar = C6H4-4-F, C6H4-4-But, C6H4-4-OMe, and C6H4-3-OMe). In addition, the pyridine-2-thiolate and pyridine-2-selenolate derivatives, [TmBut]CdSPy and [TmBut]CdSePy have been obtained via the respective reactions of [TmBut]CdMe with pyridine-2-thione and pyridine-2-selone. The molecular structures of [TmBut]CdSAr and [TmBut]CdEPy (E = S or Se) have been determined by X-ray diffraction and demonstrate that, in each case, the [CdS4] motif is distorted tetrahedral and approaches a trigonal monopyramidal geometry in which the thiolate ligand adopts an equatorial position; [TmBut]CdSPy and [TmBut]CdSePy, however, exhibit an additional long-range interaction with the pyridyl nitrogen atoms. The ability of the thiolate ligands to participate in exchange was probed by 1H and 19F nuclear magnetic resonance (NMR) spectroscopic studies of the reactions of [TmBut]CdSC6H4-4-F with ArSH (Ar = C6H4-4-But or C6H4-4-OMe), which demonstrate that (i) exchange is facile and (ii) coordination of thiolate to cadmium is most favored for the p-fluorophenyl derivative. Furthermore, a two-dimensional EXSY experiment involving [TmBut]CdSC6H4-4-F and 4-fluorothiophenol demonstrates that degenerate thiolate ligand exchange is also facile on the NMR time scale.