Anion-cation hydrogen bonding interactions are described for [(C6H11)2NH2]2[M(SC6H5)4] where M = Co (1), Zn (3), which serve as models of putative lysine-cyteine hydrogen bonding at the metal binding site of metallothionein. Complex 1 is isolated as green crystals in which an average N–H⋯S hydrogen bond length of 3.29 (1) Å is observed in infinite one-dimensional chains. The dicyclohexylammonium counterion occupies a bridging position by hydrogen bonding to thiolate ligand sulfur atoms on adjacent anion complexes. There are two [Co(SC6H5)4]2− anions per asymmetric unit where each Co atom is tetrahedrally coordinated by four benzenethiolate ligands [Co-Sav = 2.308 (4) Å]. In the non-hydrogen bonding complex [(CH3)4N)2[Co(SC6H5)4] (5), a split vibrational band at 228 cm−1 (av) is assigned to a Co-S T2 related mode. In [(CH3)4N]2[Zn(SC6H5)4] (7) this band is replaced by one at 199 cm−1. Relatively intense bands at 192 and 180 cm−1 in the Raman spectra of 1 and 3 are assigned to metal-ligand modes. Hydrogen bonding causes a decrease in metal-ligand bond length of 0.02 Å relative to the bonds in a non-hydrogen bonding complex.
ASJC Scopus subject areas
- Colloid and Surface Chemistry