Reactions of α-Diimine Ligands with the in Situ Generated “S(OTf)₂” Synthon

A series of reactions of α-diimine ligands with a 2:1 mixture of SCl2 and trimethylsilyltrifluormethanesulfonate(TMS-OTf), which behaves as an S(OTf)2 synthon, were performed. The reactivity was shown to differ based on the substitution at the nitrogen atoms of the ligand as aromatic groups yielded dicationic sulfur nitrogen heterocycles whereas alkyl groups resulted in the loss of one of the organic substituents at nitrogen giving monocationic 1,2,5-thiadiazolium rings. The substitution on the backbone carbon being a hydrogen atom, phenyl group (diazabutadiene; DAB) or acenaphthene (bisiminoacenaphthene, BIAN) proved not to be influential on the outcome of the reaction as both systems resulted in N,N′-chelated dications. These are rare examples of sulfur structural mimics of the N-heterocyclic silylene, and the BIAN species represent the first complexes of sulfur with this ubiquitous ligand.