Tetraglymes as Prochiral Host Reagents for Ammonia Borane

Abstract

The molecular structure of the complex of ammonia borane (AB) with acyclic ether tetraglyme Me(OCH 2 CH 2 ) 4 OMe (1), 1·(AB) 2 was determined by single-crystal X-ray structure analysis for the first time. The crystal structure features two AB molecules, bonded by dihydrogen bonds, per one tetraglyme unit. The intermolecular BH···HN distances of 1.94 Å are shorter than those in the solid ammonia borane (2.02-2.32 Å). A comparison of the hydrogen and dihydrogen bonds in 1·(AB) 2 and in the complexes of AB with crown-ethers (CE) was carried out. The complex formation with both the CE and the acyclic polyether 1 activates the B-H bond in AB via N-H···O hydrogen bonds * Prof. Dr. A. Y. Timoshkin E-Mail: a.y.timoshkin@spbu.ru [a]