Low temperature and paramagnetic ion effects on the proton and boron-11 nuclear magnetic resonance spectra of the triborohydride in (B3H8–)

Abstract

The disappearance of ¹¹B–H coupling is observed at low temperatures in the n.m.r. spectrum of the triborohydride ion. This phenomenon is attributed to electric quadrupole relaxation effects. Partial ¹¹B–H decoupling is also effected by the addition of the paramagnetic manganese(II) ion. Only one type of proton in the ¹H n.m.r. is observed down to –135° which allows for an upper limit of ca. 8 kcal./mole for ΔG‡ of the hydrogen tautomerization process.