Rapid reversible rearrangements in tetracyclo[4.4.4.4.]-1-boron-3,5-diazapentane

Ab initio (RHF/6-31G) calculations were used to study the degenerated isomerization of a new system tetracyclo[4.4.4.4.]-1-boron-3,5-diazapentane. The calculations showed, that suggested structure corresponded to energy minimum, boron atom formed the fourth chemical bond due to dative (donor-acceptor) interaction between a free σ(p)-orbital of boron atom and nonshared electron pair of nitrogen atom. The length of donor-acceptor bond is equal to 1.533 A. Such sufficient reduction of B -> N bond is related with sterical forcing of boron and nitrogen centers to convergence in a tense tetracyclic system. Reaction of bond reversing proceeds through transient state with crossing the activation barrier, equal to 6.67 kcal/mol. 14 refs.; 1 fig.; 1 tab