Three-dimensional aromaticity of polyhedral boranes

Aihara, Jun‐ichi

doi:10.1021/ja00479a015

Cited by 274 publications

(168 citation statements)

References 4 publications

(4 reference statements)

Supporting

Mentioning

158

Contrasting

Unclassified

Order By: Relevance

“…NICS values which are 1 A above a B 3 -face in [B 5 H 5 ] 2À are À16.7 ppm, while the center of a face is only 0.57 A off center and the cluster center itself forms part of a three-membered ring with a distance of only 0.53 A from edge to center. This means that the influence of the electron densities on edges and faces sums to a highly negative NICS value in the center and, as a result of these findings, Aihara classified [B 5 H 5 ] 2À as nonaromatic [11]. A fusion of two tetrahedrals via a common face is not permitted for boron [58]; likewise, in [Al 5 H 5 ] 2À the influence of the electron density on the faceswhich are only 0.86 A distant from the center -sums to a negative NICS in the cluster.…”

Section: Aromaticity Of [E N H N ] 2à Clustersmentioning

confidence: 99%

“…A variety of concepts has been introduced to explain the structures and stoichiometry of main-group cluster compounds, the most commonly known being the WadeWilliam-Rudolph rules [4-6]; for higher, conjugated clusters these rules were later modified by Jemmis [7,8]. Element-rich clusters [E n R m ] xÀ , especially of the heavier elements of Group 13, were classified as metalloids [2, 3].Cluster compounds such as the polyhedral boranates [B n H n ] 2À have been discussed as three-dimensional (3-D) aromatic systems [9][10][11]. According to Paul von Rague Schleyer, a diatropic ring current is the most typical property of an aromatic molecule [12].…”

mentioning

confidence: 99%

“…Cluster compounds such as the polyhedral boranates [B n H n ] 2À have been discussed as three-dimensional (3-D) aromatic systems [9][10][11]. According to Paul von Rague Schleyer, a diatropic ring current is the most typical property of an aromatic molecule [12].…”

mentioning

confidence: 99%

See 2 more Smart Citations

Cages and Clusters of Indium: Spherical Aromaticity?

Linti

Bühler

Monakhov

et al. 2011

Modeling of Molecular Properties

View full text Add to dashboard Cite

The cluster chemistry of main-group elements has developed fruitfully during the past decades [1, 2]. When focusing on the heavier Group 13 elements, aluminum and gallium clusters have been examined most extensively, showing both polyhedral [E n R n ] xÀ (n ¼ 4, 6, 8, 9, 12; x ¼ 0, 1, 2) and element-rich clusters [E n R m ] xÀ (n > m, for example n ¼ 5, 8, 9, 10, 22, 26, 77, 82) [3]. Cluster compounds of indium, despite the higher stability of low oxidation states, have been investigated only marginally. A variety of concepts has been introduced to explain the structures and stoichiometry of main-group cluster compounds, the most commonly known being the WadeWilliam-Rudolph rules [4-6]; for higher, conjugated clusters these rules were later modified by Jemmis [7,8]. Element-rich clusters [E n R m ] xÀ , especially of the heavier elements of Group 13, were classified as metalloids [2, 3].Cluster compounds such as the polyhedral boranates [B n H n ] 2À have been discussed as three-dimensional (3-D) aromatic systems [9][10][11]. According to Paul von Rague Schleyer, a diatropic ring current is the most typical property of an aromatic molecule [12]. For endohedral fullerenes, it was proved that chemical shifts for atoms in endohedral and exohedral positions behave comparable to shifts of atoms in and out of the ring plane of an aromatic hydrocarbons, respectively [13]. Aromaticity can be quantified by the calculated magnetic shielding constants at selected regions of a molecule, where no atoms reside. The resulting nucleus-independent chemical shifts (NICSs) are negative (diatropic) for aromatic molecules, positive (paratropic) for anti-aromatic molecules, and approximately zero for non-aromatic molecules [12].It has been demonstrated that the skeletal number of electrons, as well as the substituents of boron cluster compounds, influence the NICS values in the center of clusters [14]. Whilst B 8 Cl 8 and B 9 Cl 9 are well-known compounds [15], it was not possible to prepare B 8 H 8 and B 9 H 9 . According to NICS values in the cluster center, B 9 F 9 is aromatic, as well as [B 8 H 8 ] 2À [16, 17] and [B 9 H 9 ] 2À [18], a closo-cluster compound by the Wade rules. B 9 H 9 , in contrast, is paratropic, which means Modeling of Molecular Properties, First Edition. Edited by Peter Comba.

show abstract

Section: Aromaticity Of [E N H N ] 2à Clustersmentioning

confidence: 99%

mentioning

confidence: 99%

See 1 more Smart Citation

Cages and Clusters of Indium: Spherical Aromaticity?

Linti

Bühler

Monakhov

et al. 2011

Modeling of Molecular Properties

View full text Add to dashboard Cite

show abstract

“…An edge-localized polyhedron has two electron two-center bonds along each edge of the polyhedron. A globally delocalized polyhedron has a multicenter core bond in the center of the polyhedron and may be regarded as a three-dimensional "aromatic" system [27]. A complicated metal cluster system consisting of fused and/or capped polyhedra can have globally delocalized bonding in some polyhedral regions and edge-localized bonding in other polyhedral regions.…”

Section: Introductionmentioning

confidence: 99%

Graph theory in the study of metal cluster bonding topology: Applications to metal clusters having fused polyhedra

King

1986

Int. J. Quantum Chem.

View full text Add to dashboard Cite

The energy levels in a delocalized two‐ or three‐dimensional chemical structure are related to the eigenvalues of the graph representing the corresponding bonding topology. Such relatively crude but computationally undemanding graph theory‐derived models provide a clear demonstration of the close relationship between two‐dimensional aromatic systems such as benzene and three‐dimensional aromatic systems such as deltahedral boranes, carboranes, and metal clusters. The basic building blocks for the three‐dimensional aromatic systems are deltahedra, having no degree 3 vertices. Delocalized bonding in such systems having v vertices requires two electrons for a multicenter core bond as well as 2v electrons for pairwise surface bonding. A problem of particular interest is how metal cluster polyhedra can fuse together, leading ultimately to the infinite structures of the bulk metals. As a model for such processes the fusion of rhodium carbonyl octahedra is examined using graph theory‐derived methods. These lead to reasonable electron‐precise models for the bonding topologies in the “biphenyl analogue” [Rh12(CO)30]2−, the “naphthalene analogue” [Rh9(CO)19]3−, the “anthracene analogue” H2Rh12(CO)25, and the “perinaphthene analogue” [Rh11(CO)23]3−. Similar models can also be developed for clusters based on centered larger rhodium polyhedra as exemplified by the centered cuboctahedral clusters of the type [Rh13(CO)24H5–q]q− (q = 2, 3, 4) representing a fragment of the hexagonal close‐packed metal structure.

show abstract

“…The 12-vertex icosahedral cluster anion B 12 H 2À 12 is the prototype of a three-dimensional aromatic p-electron system [1][2][3][4]. The neutral carboranes o-, m-, p-C 2 B 10 H 12 and the anion CB 11 H À 12 are simple derivatives which preserve the basic features of the electronic structure of B 12 H 2À 12 .…”

mentioning

confidence: 99%