NMR of carboranes

This contribution presents a survey of the literature on the NMR of carboranes from the early years of study to the present day. Following an introduction to the subject, subsequent sections deal with the principal nuclei concerned, namely the isotopes of boron, (overwhelmingly 11 B), 1 H, 13 C and 19 F (the latter as there are many examples of clusters where terminal B-Hs are substituted by B-F units, fluorine may therefore be regarded as a significant tool in the field). Despite the title, some literature on boron clusters (carbon-free) is included where it is felt they can illuminate the topic, also metallaboranes and metallacarboranes, with similar justification. Many journal articles describing synthetic and structural studies of carboranes will heavily feature NMR as a technique of characterization. Reference to these is limited, attention being focussed on work where novel or pioneering NMR concepts and discoveries are described. Significant attention is paid to computational methods, especially in relation to 11 B NMR, and to the Antipodal Effect, a rich area of study over many years, both computationally and spectroscopically. The utility of NICS (nucleus-independent chemical shift) values in assessing three-dimensional aromaticity of some carboranes, is covered, including comparison with more conventional organic aromatics. Finally, there is included a relatively brief survey of instrumental methods, including 2D techniques, solid-state, and dynamic NMR spectroscopy. There is a vast literature on the NMR of carboranes and this chapter can only be a portal into that space, the reader is directed to the many relevant reviews, referenced in this work, for further information.