An asymmetrically substituted borazine

Abstract

The B3N3 ring in the title compound, 1,3,5-tri-tert-butyl-2,4-difluoro-6-phenylcyclotriborazane, [PhF2B3N3(t)Bu3] or C18H32B3F2N3, an asymmetrically substituted borazine, is distorted from planarity. The molecule resides on a twofold axis. The N atoms of the N-B(Ph)-N group lie on opposite sides of the least-squares plane formed by the four remaining ring atoms, due to steric accommodation of the tert-butyl groups, a conformation not previously observed for a borazine. The B-N bond lengths are in the range 1.4283 (14)-1.4493 (12) A, due to the F substituents residing on two of the B atoms, which also produce a large deviation from 120 degrees in one of the B-N-B angles [ca 113.6 (1) degrees]. The phenyl group is twisted with respect to the B3N3 ring, the interplanar angle being 62.87 (5) degrees.