Pi Bonding and Negative Hyperconjugation in Mono-, Di-, and Triaminoborane, -alane, -gallane, and -indane

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• 作者：Bethany L. Kormos and Christopher J. Cramer
• 刊名：Inorganic Chemistry
• 出版年：2003
• 出版时间：October 20, 2003
• 年：2003
• 卷：42
• 期：21
• 页码：6691 - 6700
• 全文大小：131K
• 年卷期：v.42,no.21(October 20, 2003)
• ISSN：1520-510X

文摘

A systematic quantum chemical investigation of mono-, di-, and triaminoborane, -alane, -gallane, and -indane iscarried out to determine quantitatively the effects of pi bonding and negative hyperconjugation on structures, energetics,and rotational barriers in these systems. Pi bonding plays a significant role in the aminoborane compounds, butbecomes rapidly less significant in the aminoalanes, -gallanes, and -indanes. For each main-group metal Xinvestigated, X-N rotational barriers are found to be essentially equal depending only on the number of remainingin-plane amino groups. The contribution of negative hyperconjugation to reducing rotational barriers, as assessedfrom natural bond orbital (NBO) delocalization energies, is independent of the pyramidalization of the out-of-planeamino group, and is also dependent only on the number of rotated groups. Optimized tris[bis(trimethylsilyl)amino]-substituted structures of boron, aluminum, gallium, and indium are found to compare quite well with availableexperimental structural data, and exhibit X-N torsion angles that are independent of the central metal atom.