Chapter 1 - Introduction and History

Abstract

This chapter introduces the book and deals with the history of carboranes, carborane chemistry, and its applications. Carboranes are polyhedral boron–carbon molecular clusters that are stabilized by electron-delocalized covalent bonding in the skeletal framework. In contrast to classical organoboranes such as borabenzene (C5H5B), the skeletal carbon atoms in carboranes typically have at least three and as many as five or six neighbors in the cluster, forming stable—in some cases, exceedingly stable—molecular structures. Carboranes were envisioned from theoretical considerations before reports of the synthesis of any such compounds appeared; although it is entirely possible that they may have been present in some CxByHz products generated by experimentalists. The first icosahedral carboranes had actually been prepared in industrial laboratories in the 1950s but were kept under wraps and not reported in the open literature until late 1963. Carborane chemistry is experiencing a major surge in interest across a wide spectrum of technologies, fueled by developing applications in medicine, nanoscale engineering, catalysis, metal recovery from radioactive waste, and a number of other areas, documented in thousands of publications and patents. This resurgence has been ignited by a wide (if belated) recognition of the unique electronic properties, geometry, and extraordinary versatility of carboranes, and a growing recognition that carborane chemistry affords a whole new realm of possibilities that transcends conventional organic or organometallic synthesis. Their extraordinary ability (shared with polyhedral boranes in general) to accommodate metal and nonmetal atoms of nearly every description in the cage framework has so far-reaching potential and significance that it impacts virtually every field of chemistry.