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Tetraglymes as Prochiral Host Reagents for Ammonia Borane
Author(s) -
Shelyganov Pavel A.,
Virovets Alexander,
Peresypkina Eugenia,
Scheer Manfred,
Timoshkin Alexey Y.
Publication year - 2019
Publication title -
zeitschrift für anorganische und allgemeine chemie
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.354
H-Index - 66
eISSN - 1521-3749
pISSN - 0044-2313
DOI - 10.1002/zaac.201800333
Subject(s) - chemistry , ammonia borane , steric effects , hydrogen bond , diastereomer , borane , molecule , ether , crystal structure , stereochemistry , crystallography , medicinal chemistry , computational chemistry , hydrogen , organic chemistry , catalysis , hydrogen storage
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 and therefore increases the reducing activity of AB. Supposedly, the structure of 1· (AB) 2 is related to the initial steps of the AB activation in a polyether solution. The effect of the substituents on the complexation of the substituted derivatives of 1 comes down to a structural adjustment minimizing steric repulsion. Computations reveal that the complexation of diastereomeric disubstituted glymes with AB leads to the formation of diastereomeric complexes that differ noticeably in stability. This is a prerequisite for inducing stereoselectivity, which makes such complexes attractive for potential synthetic applications.