MATRIX-ISOLATION STUDY OF THE REACTIONS OF B2H6 WITH PYRIDINE, PYRROLE, AND PYRROLIDINE - SPECTROSCOPIC CHARACTERIZATION OF C4H9N.BH3 AND C4H8N=BH2

The products of the pyrolytic reaction of B2H6 With pyrrole, pyrrolidine, and pyridine have been isolated in argon matrices at 14 K and characterized by infrared spectroscopy. For the B2H6/C4H9N system, complex formation was observed at temperatures between ambient and 200-degrees-C and the subsequent H-2 elimination product H2B=NC4H8 at pyrolysis temperatures above 50-degrees-C. The B=N stretching frequency (1486 cm-1) and local density functional calculations done in support of the experiments both support substantial double-bond character for the boron-nitrogen bond. The reaction of B2H6 with pyridine led to formation of the H3B.NC5H5 complex only, while copyrolysis of B2H6 with pyrrole led to no reaction even when a pyrolysis temperature of 380-degrees-C was employed. This result is best understood in terms of the role of the nitrogen lone pair in the aromaticity of the pyrrole ring.