Symmetrical exchange of potassium trialkylborohydrides with trialkylboranes, direct observation of steric effects by ¹¹B NMR spectroscopy

Mixtures of potassium triethylborohydride and triethylborane in tetrahydrofuran at 25° C show evidence by 11B NMR and IR spectroscopy of essentially quantitative formation of a hydride bridged diborohydride ion and of rapid exchange between diboron and monoboron species. The formation of an association compound (2/1) and the rate of hydride exchange is remarkably sensitive to increases in steric hindrance of the alkyl groups on boron. © 1978.