The Molecular Structure of 1,3,5,7-Tetra(tert-butyl)-2,4,6,8-tetraazido-borazocine [1]

The tetra(tert-butyl)-tetraazido-borazocine, 1, has the expected tub shape as determined for (SCNB=NtBU)(4). However, it crystallizes in the triclinic system and shows no symmetry element in contrast to the isothiocyanato derivate which has C-2 symmetry. There are two kinds of BN bonds which alter from long to short (average 1.491 and 1.388 angstrom). The BN bond lengths to the azido groups are, on average, 1.486 angstrom. All B and N atoms of the ring reside in a trigonal planar environment. The B-N-N bond angles are close to 120 degrees showing that the central nitrogen atom can be considered as sp(2)-hybridized. The N-N-N bond angles Lire on average 173.6 degrees. The two sets of the opposite B2N2 planes include an angle of 114.8 degrees. The atoms of the azido groups are almost coplanar with the respective NBN planes. This together with the short BN(N-2) bond lengths indicates that these azido groups are pi-bonded to their corresponding boron atom.