Beyond the Hawthorne Reaction: Li Induced Thermal Dehydrocoupling of -10-vertex Carborane Anions.

In the 1970s Hawthorne reported an electrochemical dehydrocoupling reaction of the -carborane anion [HCBH] to form the biscarborane [CBH] . In this Communication we show that the said "Hawthorne Reaction" can be achieved thermally and that it tolerates C-butylation. The new compound was fully characterized by B, H, and C NMR spectroscopies, high-resolution mass spectrometry, and single-crystal X-ray diffraction. One interesting caveat is that or only form thermally when they are salts of Li and not NEt, Na, K, or Cs. This observation means that Li in some way facilitates this process, introducing a new kind of Li effect.