Aldiminium and 1,2,3-triazolium dithiocarboxylate zwitterions derived from cyclic (alkyl)(amino) and mesoionic carbenes

Abstract

The synthesis of zwitterionic dithiocarboxylate adducts was achieved by deprotonating various aldiminium or 1,2,3-triazolium salts with a strong base, followed by the nucleophilic addition of the in situ-generated cyclic (alkyl)(amino) or mesoionic carbenes (CAACs or MICs) onto carbon disulfide. Nine novel compounds were isolated and fully characterized by 1H and 13C NMR, FTIR, and HRMS techniques. Moreover, the molecular structures of two CAAC·CS2 and two MIC·CS2 betaines were determined by X-ray diffraction analysis. The analytical data recorded for all these adducts were compared with those reported previously for related NHC·CS2 betaines derived from imidazolinium or (benz)imidazolium salts. Due to the absence of electronic communication between the CS2 unit and the orthogonal heterocycle, all the CAAC·CS2, MIC·CS2, and NHC·CS2 zwitterions displayed similar electronic properties and featured the same bite angle. Yet, their steric properties are liable to ample modifications by varying the exact nature of their cationic heterocycle and its substituents.

Homoleptic ruthenium(ii) complexes bearing imidazol(in)ium-2-dithiocarboxylate ligands: synthesis, characterization, and redox properties

“…1 Reacting CS 2 with a free carbene, either preformed or generated in situ by deprotonating an azolium salt with a strong base, is indeed the most common strategy to obtain these betaines (Scheme 1B). 2,3 Yet, back in 1965, Winberg and Coffman isolated the first representatives of these inner salts upon cleavage of enetetramines with CS 2 in xylenes (Scheme 1A). 4 More recently, we showed that (benz)imidazol(in)ium-2-dithiocarboxylates could also be readily obtained from their azolium salt precursors and CS 2 using cesium carbonate as a weak inorganic base under mild aerobic conditions, thereby avoiding the intermediacy of air-and moisture-sensitive NHCs (Scheme 1C).…”