Aluminum-poor hexacarbalane structures: The transition from localized organoaluminum structures to delocalized polyhedra

作者：Attia Amr A A; Lupan Alexandru^*; King Robert Bruce^*

来源：International Journal of Quantum Chemistry, 2018, 118(6): e25506.

DOI：10.1002/qua.25506

• aluminum
• delocalized polyhedra
• density functional theory
• hexacarbalanes
• localized organoaluminum structures

The series of hexacarbalanes C6Aln-6Men (n=7-11) represent a progression from localized organoaluminum structures to delocalized polyhedral structures en route to experimentally known 13- and 14-vertex hexacarbalanes such as (AlMe)(8)(CCH2Ph)(5)(mu H-4), (AlMe)(8)(CCH2Ph)(5)(CCPh), [R4N+](2)[(AlH)(8)(CR)(6)], and (AlNMe3)(2)(AlR)(6)(CR)(6). In this connection, the lowest energy seven-vertex C6AlMe7 structure has a tetrahapto benzene ring with the four AlC(cage) bonding interactions required to give the aluminum the favored octet configuration. Related eight-vertex C6Al2Me8 structures are found with a benzene ring bound to an Al-2 unit with a short AlAl distance of approximate to 2.55 angstrom suggesting a formal double bond. However, the lowest energy C6Al2Me8 structure has a dialuminacyclobutene unit fused to a tricyclohexane unit through an Al-2 edge. Other relatively low-energy C6AlMe7 and C6Al2Me8 structures consist of a six-carbon hexatriene chain either forming a seven-membered C6Al ring in the seven-vertex structure or acting as a flyover between an Al-2 unit. The lowest energy nine-vertex hexacarbalane C6Al3Me9 has two separate C-3 units bridged by both an Al-2 pair and a single aluminum atom. Higher energy C6Al3Me9 hexacarbalanes contain a pentadienyl chain and an isolated carbon atom with an imbedded bonded Al-3 triangle. The low-energy 10-vertex C6Al4Me10 structures have a central Al-4 butterfly with nonbonding distances between the wingtips ranging from 3.35 to 3.91 angstrom. The lowest energy 11-vertex C6Al5Me11 structure has a central Al-4 quadrilateral with a diagonal bridged by the fifth aluminum atom. Higher energy C6Al5Me11 structures have an edge rather than a diagonal of the central Al-4 quadrilateral bridged by the fifth aluminum atom.

• 出版日期2018-3-15