Crystal data behind efficient cesium recognition: triphenylcyanoborates of potassium, rubidium, and cesium

Crystal structures of potassium, rubidium, and cesium triphenylcyanoborates were investigated in order to explain high selectivity of triphenylcyanoborate ion (“caesignost”) as an agent for cesium precipitation. Alkali metal ions have substantially different coordination modes with triphenylcyanoborate ion coordinated to the cyano group in the end-on or side-on motif and to the phenyl group in the π–M+ motif.