caa a22 4500 465754600 CHVBK 20180323111843.0 cr unu---uuuuu 170327e19901201xx s 000 0 eng 10.1007/BF01170005 doi (NATIONALLICENCE)springer-10.1007/BF01170005 King R. Department of Chemistry, University of Georgia, 30602, Athens, Georgia, USA aut Three-dimensional aromaticity: A topological analysis of computational methods [Elektronische Daten] [R. King] The deltahedral boranes B n H n 2− (6 ≤n ≤ 12) may be regarded as three-dimensional delocalized aromatic systems in which surface bonding and core bonding correspond to σ-bonding andπ-bonding, respectively, in planar polygonal two-dimensional hydrocarbons C n H n (n − 6)+ (n = 5, 6, 7). The two extreme types of topologies which may be used to model core bonding in deltahedral boranes are the deltahedral (D n) topology based on the 1-skeleton of the underlying deltahedron and the complete (K n) topology based on the corresponding complete graph. Symmetry factoring of generalized graphs representing the core-bonding interactions in the highly symmetrical octahedral borane B6 H6 and icosahedral borane B12H 12 2− leads to methods for separating the effects of core and surface bonding in molecular orbital energy parameters. Such analyses of the Hoffmann—Lipscomb LCAO-MO extended Mickel computations, the Armstrong—Perkins—Stewart self-consistent molecular orbital computations, and SCF MO ab initio Guassian 82 computations on B6H 6 2− and B12H 12 2− indicate that the approximation of atomic orbitals by a sum of Gaussians, as is typical in modem ab initio computations, leads to significantly weaker apparent core bonding approximated more closely by deltahedral (D n) rather than complete (K n) topology. Furthermore, theT 1u core orbitals which, if pure, would be nonbonding in octahedral (D 6) core topology for B6 H 6 2− and bonding in icosahedral (D12) core topology for B12H 12 2− , become antibonding through strong core—surface mixing. Because of this, the simpler graph-theory derived model for deltahedral boranes using complete (K n) core bonding topology gives the correct numbers of bonding orbitals even in cases where the complete graphK n is a poor approximation for the actual core bonding topology. J.C. Baltzer AG, Scientific Publishing Company, 1990 Journal of Mathematical Chemistry Kluwer Academic Publishers 4/1(1990-12-01), 69-85 0259-9791 4:1<69 1990 4 10910 https://doi.org/10.1007/BF01170005 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/BF01170005 text/html Onlinezugriff via DOI NATIONALLICENCE 100 1- King R. Department of Chemistry, University of Georgia, 30602, Athens, Georgia, USA aut NATIONALLICENCE 773 0- Journal of Mathematical Chemistry Kluwer Academic Publishers 4/1(1990-12-01), 69-85 0259-9791 4:1<69 1990 4 10910 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer