1,1/1,2 Isomerisation in Lewis base adducts of B2cat2

Abstract

Reaction of bis-catecholatodiborane and 1 or 2 equivalents of 1,5-diazabicyclo[4.3.0]non-5-ene or 4-picoline yields Lewis acid–base adducts. Recrystallisation enabled identification of an unexpected isomerisation from the 1,1-isomer to the 1,2-isomer. This observation was probed computationally with significantly different dipole moments calculated for the two effectively isoenergetic isomeric forms.