Tetraamine Me₆TREN induced monomerization of alkali metal borohydrides and aluminohydrides

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• 作者：Alan R. Kennedy ; Ross McLellan ; Greg J. McNeil ; Robert E. Mulvey ; ^{r.e.mulvey@strath.ac.uk" class="auth_mail" title="E-mail the corresponding author} ; Stuart D. Robertson ; ^{stuart.d.robertson@strath.ac.uk" class="auth_mail" title="E-mail the corresponding author}
• 关键词：Alkali-metal ; Borohydride ; Aluminohydride ; Structure elucidation ; NMR spectroscopy
• 刊名：Polyhedron
• 出版年：2016
• 出版时间：8 January 2016
• 年：2016
• 卷：103
• 期：part_PA
• 页码：94-99
• 全文大小：741 K

文摘

Monomeric 1:1 complexes of MEH₄ (M, E = Li, B, 1; Na, B, 2; Li, Al, 3; Na, Al, 4) and the tripodal tetradentate ligand (Me₂NCH₂CH₂)₃N (Me₆TREN) have been prepared in good yields by refluxing in THF and allowing the solutions to cool slowly. X-ray diffraction studies show that the BH₄ group binds to either Li or Na via three hydride bridges while the AlH₄ group connects to Li via a single hydride bridge. Surprisingly, Me₆TREN·LiAlH₄ represents the first monomeric contacted ion pair LiAlH₄ derivative to be structurally characterized. In every case the tetraamine coordinates via all four of its Lewis basic nitrogen atoms. A similar protocol using the alkyl-rich borohydride MBEt₃H also gives monomeric species (M = Li, 5; Na, 6). All complexes have been characterized in solution by multinuclear (¹H, ⁷Li, ¹¹B, ¹³C and ²⁷Al, where appropriate) NMR spectroscopy which reveals excellent textbook examples of ¹J coupling between B/Al and H in the cases of complexes 1–4 and between B and C in the cases of complexes 5 and 6.