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 [Tm-But]CdSAr, have been synthesized by the reactions of [Tm-But] CdMe with ArSH (Ar = C6H4-4-F, C6H4-4-Bu-t, C6H4-4-OMe, and C6H4-3-OMe). In addition, the pyridine-2-thiolate and pyridine-2-selenolate derivatives, [Tm-But]CdSPy and [TmBut]-CdSePy have been obtained via the respective reactions of [Tm-But] CdMe with pyridine-2-thione and pyridine-2-selone. The molecular structures of [Tm-But]CdSAr and [Tm-But] (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; [Tm-But] CdSPy and [Tm-But]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 H-1 and F-19 nuclear magnetic resonance (NMR) spectroscopic studies of the reactions of [Tm-But CdSC6H4-4-F with ArSH (Ar = C6H4-4-Bu-t 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 [Tm-But]CdSC6H4-4-F and 4-fluorothiophenol demonstrates that degenerate thiolate ligand exchange is also facile on the NMR time scale.