Reactions of Amine– and Phosphane–Borane Adducts with Frustrated Lewis Pair Combinations of Group 14 Triflates and Sterically Hindered Nitrogen Bases
✍ Scribed by George R. Whittell; Edward I. Balmond; Alasdair P. M. Robertson; Sanjib K. Patra; Mairi F. Haddow; Ian Manners
- Publisher
- John Wiley and Sons
- Year
- 2010
- Tongue
- English
- Weight
- 309 KB
- Volume
- 2010
- Category
- Article
- ISSN
- 1434-1948
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✦ Synopsis
The ability of trialkyl Group 14 triflates in combination with amine and pyridine bases to dehydrogenate amine-and phosphane-borane adducts has been investigated. By using multinuclear NMR spectroscopy, it has been shown that Me 2 NH•BH 3 ( ) is efficiently converted to [Me 2 N-BH 2 ] 2 ( ) by the so-called "frustrated Lewis pair" (FLP) of nBu 3 SnOTf (4, -OTf = -OSO 2 CF 3 ) and 2,2,6,6-tetramethylpiperidine (6). Within the scope of the study, exchange of the Lewis acid effects the rate of dehydrogenation in the order: 4 Ͼ Me 3 Si-OTf (2) Ͼ Et 3 SiOTf (3). Exchange of the Lewis base for 2,6di-tert-butylpyridine (5) has also been shown to reduce the rate of reaction, whereas 1,3-di-tert-butylimidazol-2-ylidene (7) reacted directly with 2 to afford 1,3-bis-tert-butyl-4-(trimethylsilyl)imidazolium triflate (8[OTf]). For FLP combina-