Synthesis of N,C Bound Sulfur, Selenium, and Tellurium Heterocycles via the Reaction of Chalcogen Halides with −CH3 Substituted Diazabutadiene Ligands

A series of N,C bound chalcogen heterocycles from the reaction of chalcogen halides (ChX n ; Ch = S, Se Te; X = Cl, Br; n = 2, 4) with N-alkyl or N-aryl 1,4-diazabutadiene (DAB) ligands featuring methyl substituents on the backbone C−C linkage are reported. In contrast to what is observed for other p-block elements with the same ligand systems, which typically bind in an N,N′ fashion, the chalcogens react with the ligand in an unusual manner, forming N1C3Ch1 five-membered rings by incorporating a “backbone” methyl group. Solid state structures of the feature compounds have been confirmed by X-ray crystallographic studies. The reaction mechanism was probed by deuterium isotope labeling of the DAB ligand and analyzed using stopped-flow kinetics experiments, which supported attack by the olefin in the enamine form of the DAB ligand with concomitant loss of HX.