The molecular structure of the tris(2-mercapto-1-tolylimidazolyl)hydroborato zinc(2-mercapto-1-tolylimidazole) complex, {[Tmp-Tol]Zn(mim(p-Tol))}[ClO4]: intermolecular N-H center dot center dot center dot OClO3 versus intramolecular N-H center dot center dot center dot S hydrogen bonding interactions of the mercaptoimidazole ligand

The molecular structure of the tris(2-mercapto-1-tolylimidazolyl) hydroborato complex {[Tmp-Tol]Zn(mim(p-Tol))}[ClO4].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 [ClO4](-) counterion, {[Tmp-Tol]Zn(mim(p-Tol))...(OClO3)}, rather than hydrogen bond with a sulfur of the [Tmp-Tol] ligand. DFT calculations on a series of related complexes, namely {[Tm-Me]Zn(mim(Me))}(+), {[Tm-Me]Zn(mim(Me))}...(OClO3)}, {[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 [ClO4](-). 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.