Synthesis and crystal structures of two 1,3-di(alkyloxy)-2-(methylsulfanyl)imidazolium tetrafluoridoborates

Abstract

Two salts were prepared by methylation of the respective imidazoline-2-thione at the sulfur atom, using Meerwein's salt (trimethyloxonium tetrafluoridoborate) in CH2Cl2. 1,3-Dimethoxy-2-(methylsulfanyl)imidazolium tetrafluoridoborate (1), C6H11N2O2S+·BF4 −, displays a syn conformation of its two methoxy groups relative to each other whereas the two benzyloxy groups present in 1,3-dibenzyloxy-2-(methylsulfanyl)imidazolium tetrafluoridoborate (2), C18H19N2O2S+·BF4 −, adopt an anti conformation. In the molecules of 1 and 2, the methylsulfanyl group is rotated out of the plane of the respective heterocyclic ring. In both crystal structures, intermolecular interactions are dominated by C—H...F—B contacts, leading to three-dimensional networks. The tetrafluoridoborate counter-ion of 2 is disordered over three orientations (occupancy ratio 0.42:0.34:0.24), which are related by rotation about one of the B—F bonds.