Organic Selenocyanates as Halide Receptors: From Chelation to One-Dimensional Systems

Abstract

Organic selenocyanates were recently identified as strong chalcogen bond donors. They also play an important role in biochemistry. Here, we show that 1,2-bis(selenocyanatomethyl)benzene (1) and 1,2,4,5-tetrakis(selenocyanatomethyl)-benzene (2) crystallize from dimethylformamide (DMF) to afford solvates where two ortho-SeCN moieties act as a chelate toward the carbonyl oxygen atom of DMF through strong Se···O chalcogen bonds. This result led us to explore their ability to also chelate halide anions (Cl–, Br–) in solution as well as in the solid state, an important issue in view of applications in crystal engineering or organocatalysis. NMR titration experiments provide an association constant between 1 and Cl– of 148 M–1. We also observed the recurrent formation of cocrystal salts from the association of the ChB donors 1 and 2 with the onium salts Ph4PCl, Ph4PBr, and Bu4NCl. We demonstrate that not only μ2-halide but also μ4-halide structures can be stabilized though ChB interactions, leading to the format...