Infrared Hole Burning and Conformational Change in a Borane−Ammonia Complex

Abstract

The N-D stretching region in the infrared spectrum of the ammonia complex of tris-(2-methoxymethyl-phenol)-borane containing one D atom has been examined. The N-D bands have been hole burned, and the resulting spectra reveal the reorientation kinetics of the ammonia. The ammonia is hydrogen bonded with the bond distances and reorientation barrier typical of other compounds. The N-D stretching frequencies are higher than those of comparison compounds.

Infrared Hole Burning of Crown Ether 18-c-6 Ammonium Ion Complexes

“…We have found some examples of more complicated ammine compounds such as the complex with a substituted borane. 6 This latter complex is similar to those of the amino acid salts, which we have also been able to burn, 5 since the nitrogen is bonded to only three hydrogen atoms rather than four. Not all ammonium compounds will hole burn under the conditions of our experiments; the barriers to rotation of the nitrogen moiety must be in the range of 8-24 kJ/mol.…”

“…These complexes seem quite different from most of the simpler ammonium compounds that we have studied previously. We have found some examples of more complicated ammine compounds such as the complex with a substituted borane . This latter complex is similar to those of the amino acid salts, which we have also been able to burn, since the nitrogen is bonded to only three hydrogen atoms rather than four.…”

“…The compounds we have previously investigated include numerous ammonium salts as well as compounds containing the NH 3 + moiety such as amino acid salts. 5 Another noteworthy complex is between ammonia and a substituted borane 6 in which the ammonia is hydrogen bonded to three oxygen atoms of the borane and the fourth coordinating position is occupied by a nitrogen-boron bond.…”