The molecular structure of the tris(2-mercapto-1-tolylimidazolyl)hydroborato zinc(2-mercapto-1-tolylimidazole) complex, [[Tm(p-Tol)]Zn(mim(p-Tol))][ClO4]: intermolecular N-H...OClO3versus intramolecular N-H...S hydrogen bonding interactions of the mercaptoimidazole ligand

The molecular structure of the tris(2-mercapto-1-tolylimidazolyl)hydroborato complex [[Tm(p-Tol)]Zn(mim(p-Tol))][ClO(4)].3MeCN has been determined by X-ray diffraction, thereby demonstrating that the mim(p-Tol) ligand exhibits a N-H...O hydrogen bond with the [ClO(4)](-) counterion, [[Tm(p-Tol)]Zn(mim(p-Tol))...(OClO(3))], rather than hydrogen bond with a sulfur of the [Tm(p-Tol)] ligand. DFT calculations on a series of related complexes, namely [[Tm(Me)]Zn(mim(Me))](+), [[Tm(Me)]Zn(mim(Me))]...(OClO(3))], [[Tm(Me)]Zn(mim(Me))]...[O(H)Me]](+), and [[Tm(Me)]Zn(mim(Me))]...(NCMe)](+) demonstrate that an intramolecular N-H...S hydrogen bond within [[Tm(Me)]Zn(mim(Me))](+) is also less favored than the corresponding hydrogen bonding interactions with MeCN, MeOH, and [ClO(4)](-). The inability of the sulfur atoms of [Tm(R)] ligand to act as an effective hydrogen bond acceptor is in marked contrast to the ability of sulfur atoms in thiolate ligands to participate in the formation of N-H...S hydrogen bonds, an observation that reflects the "thione"versus"thiolate" nature of the [Tm(R)] ligand.