2-Chlorovinyl Tellurium Dihalides, (p-tol)Te[C(H)=C(Cl)Ph]X-2 for X = Cl, Br and I: Variable Coordination Environments, Supramolecular Structures and Docking Studies in Cathepsin B

Crystallography shows that the Te atom in each of (p-tol)Te[C(H)=C(Cl)Ph]X-2, for X = Cl (1), Br (2) and I (3), is within a distorted Psi-pentagonal bipyramidal geometry. An E configuration for the vinyl group in (1) precludes the formation of an intramolecular Te center dot center dot center dot Cl interaction so that an intramolecular Te center dot center dot center dot pi interaction is found instead. The coordination environment features a linear Cl-Te-Cl arrangement with the pentagonal plane defined by the two C atoms of the organic substituents, an intermolecular Te center dot center dot center dot Cl contact, a Te center dot center dot center dot pi interaction and a stereochemically active lone pair of electrons. In the X = Br (2) and I (3) structures, similar coordination geometries are found but the Te center dot center dot center dot pi contact is replaced by an intramolecular Te center dot center dot center dot Cl contact owing to the adoption of a Z configuration about the vinyl bond. The differences in structure are readily explained in terms of electronic effects. Docking studies of cathepsin B with (1')-(3'), i.e. 1-3 less one Te-bound halide, show efficient binding through the agency of covalent Te-S-Cys29 bonds with stabilization afforded by a combination of N-H center dot center dot center dot pi, C-H center dot center dot center dot pi and Cl-vinyl center dot center dot center dot H interactions. These results comparable favorably with known inhibitors of cathepsin B suggesting the title compounds have potential biological activity.