On the Coordination Role of Pyridyl-Nitrogen in the Structural Chemistry of Pyridyl-Substituted Dithiocarbamate Ligands

Edward R.T Tiekink

doi:10.3390/cryst11030286

Abstract

A search of the Cambridge Structural Database was conducted for pyridyl-substituted dithiocarbamate ligands. This entailed molecules containing both an NCS2− residue and pyridyl group(s), in order to study their complexation behavior in their transition metal and main group element crystals, i.e., d- and p-block elements. In all, 73 different structures were identified with 30 distinct dithiocarbamate ligands. As a general observation, the structures of the transition metal dithiocarbamates resembled those of their non-pyridyl derivatives, there being no role for the pyridyl-nitrogen atom in coordination. While the same is true for many main group element dithiocarbamates, a far greater role for coordination of the pyridyl-nitrogen atoms was evident, in particular, for the heavier elements. The participation of pyridyl-nitrogen in coordination often leads to the formation of dimeric aggregates but also one-dimensional chains and two-dimensional arrays. Capricious behaviour in closely related species that adopted very different architectures is noted. Sometimes different molecules comprising the asymmetric-unit of a crystal behave differently. The foregoing suggests this to be an area in early development and is a fertile avenue for systematic research for probing further crystallization outcomes and for the rational generation of supramolecular architectures.

Highlights

In their most common form, dithiocarbamate ligands are mono-anionic ligands of the general formula − S2 CNR2, for R = alkyl, aryl
Notwithstanding the utility of dithiocarbamates in materials chemistry, medicine, lubricating oils, etc., here, the focus is upon the structural chemistry of a specific class of multi-functional dithiocarbamate ligands, namely pyridyl-substituted dithiocarbamate ligands
The reaction to form − S2 CNR2 is facile and the range of ligands that can be generated is only limited by the availability of the amine, both secondary (Scheme 1, Equation (1)) and primary (Scheme 1, Equation (2)), where the latter generates − S2 CN(H)R; the coordination chemistry of − S2 CNH2 is relatively limited [6,7]

Summary

Introduction

In their most common form, dithiocarbamate ligands are mono-anionic ligands of the general formula − S2 CNR2 , for R = alkyl, aryl These are readily prepared from the reaction of a secondary amine and carbon disulfide in the presence of a base, for example, an alkali hydroxide. A relevant example of this idea is the reaction of piperazine with two equivalents of carbon disulfide to form the piperazine bis(dithiocarbamate) ligand, i.e., − S2 CN(CH2 CH2 ) NCS2 −. Complexation of this with metal salts can be anticipated to result in di-nuclear molecules, and experience

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Conclusion