The complex salts CdL4(O3SCF3)2 (L = 2(1H)-pyridinethione (Py2SH), 4(1H)-pyridinethione (Py4SH), or 2(1H)-quinolinethione (Q2SH)) have been synthesized by the stoichiometric reaction of Cd(O3SCF3)2 and the appropriate thione. Both ambient-temperature 13C and reduced-temperature 111Cd NMR of CdL4(O3SCF3)2 in solution are consistent with L being bound through sulfur. Reduced-temperature NMR (31P, 77Se, 111Cd, as appropriate) of mixtures of CdL4(O3SCF3)2 and Cd(EPCy3)4(O3SCF3)2 (E = Se, Cy = c-C6H11) and of Cd(EPCy3)4(O3SCF3)2 (E = S, Se) and L in solution provides evidence for various [CdLn(EPCy3)4-n]2+. Similarly, reduced-temperature metal NMR of [CdL4]2+ and [CdL'4]2+ (L, L' = Py2SH, Py4SH, Q2SH; L not equal L') in solution shows the formation of [CdLnL'4-n]2+. Thus it has been demonstrated that at reduced temperature [CdL4]2+ is intact in solution and exchange of L is slow on the timescale of the metal chemical shift differences. From the NMR studies of Cd(EPCy3)4(O3SCF3)2 (E = S, Se):L mixtures, the binding preferences are found to be L > EPCy3 in solution. Similarly, from the reduced temperature metal NMR spectra of mixtures where L and L' compete for Cd(II) in solution, the binding preferences are Py4SH > Py2SH > Q2SH. The structure of Cd(Py2SH)4(NO3)2 (4) has been determined by single crystal X-ray analysis. Colorless crystals of 4 are tetragonal, I4(1)/acd with 8 molecules per unit cell of dimensions a = 18.660(3), c = 15.215(3) Å. The structure is comprised of recognizable NO3- anions and [Cd(Py2SH)4]2+ cations. In the cations, which have S4 symmetry, the ligands are S-bound. A network of NH···O hydrogen bonds links the cations and anions.Key words: aromatic heterocyclic thiones, cadmium complexes, phosphine chalcogenides, 111Cd, 31P, 77Se NMR, X-ray crystallography.
Electron-Deficient Acetylenes as Three-Modal Adjuvants in SNH Reaction of Pyridinoids with Phosphorus Nucleophiles
