Unexpected Stability of Al 4 H 6 : A Borane Analog?

• Published in: Science (American Association for the Advancement of Science) Vol. 315; no. 5810; pp. 356 - 358
• Main Authors: Li, X., Grubisic, A., Stokes, S. T., Cordes, J., Ganteför, G. F., Bowen, K. H., Kiran, B., Willis, M., Jena, P., Burgert, R., Schnöckel, H.
• Format: Journal Article
• Language: English
• Published: 19-01-2007
• ISSN: 0036-8075; 1095-9203
• DOI: 10.1126/science.1133767

Whereas boron has many hydrides, aluminum has been thought to exhibit relatively few. A combined anion photoelectron and density functional theory computational study of the Al
4
H
–
6
anion and its corresponding neutral, Al
4
H
6
, showed that Al
4
H
6
can be understood in terms of the Wade-Mingos rules for electron counting, suggesting that it may be a borane analog. The data support an Al
4
H
6
structure with a distorted tetrahedral aluminum atom framework, four terminal Al-H bonds, and two sets of counter-positioned Al-H-Al bridging bonds. The large gap between the highest occupied and the lowest unoccupied molecular orbitals found for Al
4
H
6
, together with its exceptionally high heat of combustion, further suggests that Al
4
H
6
may be an important energetic material if it can be prepared in bulk.