Historical and Recent Developments in the Chemistry of Cyanate Congeners

The cyanate anion, [OCN]^-, and its heavier congeners with the general formula [ChCPn]^- (Ch = O-Te, and Pn = N-As) are fundamental in introductory chemistry textbooks, chemical laboratories worldwide, and modern research. Their discovery spans more than 200 years and includes key milestones in the history of chemistry, e.g., concepts of isomerism and pseudohalogens. Today, in particular, heavy pnictogen congeners are valued as versatile building blocks for chemical transformations and the synthesis of a multitude of exciting new compounds. Given the importance of these anions in history and recent chemistry, this Review first explores the historical development of these anions starting from the very beginning of the modern chemical literature (1800s) until today. This section is followed by an in-depth summary and comparison of their electronic structures leading to their development into vital building blocks for chemical transformations. Finally, we present a comprehensive state-of-the-art overview of the chemistry of the heaviest congeners, emphasizing the vast opportunities that these fascinating anions offer to contemporary chemists.