Planar Tetracoordinate Carbons in Cyclic Hydrocarbons

Pérez, Netzahualcóyotl Mayek; Heine, Thomas; Barthel, Robert; Seifert, Gotthard; Vela, Alberto; Méndez‐Rojas, Miguel A.; Merino, Gabriel

doi:10.1021/ol050170m

Cited by 70 publications

(64 citation statements)

References 39 publications

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“…[44] More isoelectronic analogues of the structures in Schemes 4a nd 5w ere designed by Sastry and co-workers. [45] Subsequently,M erino and co-workers [44,46] reported as eries of ptC-containing cyclic hydrocarbons (16 a-h; Figure 16). These molecules were created by combining the C 5 2À skeleton with cyclic hydrocarbon fragments.A lmost at the same time,E steves and co-workers [47] analyzed the spiropentadiene dication and concluded that the ptC is mainly stabilized by s electrons and that the ptC has an egative charge.T he total positive charge is spread along the skeleton structure.M oreover,t he spiropentadiene dication has a2 .3 kcal mol À1 activation barrier for ring opening.…”

Section: +mentioning

confidence: 99%

Four Decades of the Chemistry of Planar Hypercoordinate Compounds

et al. 2015

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The idea of planar tetracoordinate carbon (ptC) was considered implausible for a hundred years after 1874. Examples of ptC were then predicted computationally and realized experimentally. Both electronic and mechanical (e.g., small rings and cages) effects stabilize these unusual bonding arrangements. Concepts based on the bonding motifs of planar methane and the planar methane dication can be extended to give planar hypercoordinate structures of other chemical elements. Numerous planar configurations of various central atoms (main-group and transition-metal elements) with coordination numbers up to ten are discussed herein. The evolution of such planar configurations from small molecules to clusters, to nanospecies and to bulk solids is delineated. Some experimentally fabricated planar materials have been shown to possess unusual electrical and magnetic properties. A fundamental understanding of planar hypercoordinate chemistry and its potential will help guide its future development.

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Section: +mentioning

confidence: 99%

Four Decades of the Chemistry of Planar Hypercoordinate Compounds

et al. 2015

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“…The induced fields are either in line with the applied field, hence increasing it (paratropic) for anti-aromatic compounds, or against the field, shielding it (diatropic) for aromatic compounds. The induced magnetic field analysis has been applied recently to understand the electronic properties of compounds containing a planar tetracoordinate carbon [44,45], aluminum clusters [46], and studies of other systems, including conjugated double rings, are in progress.…”

Section: Computational Detailsmentioning

confidence: 99%

Borazine: to be or not to be aromatic

et al. 2007

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Aromaticity of borazine, which has been subject of controversial discussions, is addressed. Beside a short review on aromaticity of borazine we report a detailed analysis of two molecular fields, the induced magnetic field (B ind ) and the electron localization function (ELF). The induced magnetic field of borazine shows a long-range shielding cone perpendicular to the molecular plane, as in benzene, but lower in magnitude. Contrary to benzene, borazine shows two weakly paratropic regions, one of them inside the ring, and the second one enveloping the boron atoms. It is necessary to separate r and p contributions to identify whether borazine exhibits p-aromatic character comparable to benzene. Nucleus-independent chemical shift (NICS) isolines show that the r electrons are much stronger localized than p electrons, their local paramagnetic contributions generate a short-range response and a paratropic (deshielding) region in the ring center (similar to an anti-aromatic response). Three regions can be identified as chemically meaningful domains exhibiting an internally strong electron delocalization (ELF = 0.823). Borazine may be described as a p aromatic compound, but it is not a globally aromatic species, as the electronic system is not as delocalized as in benzene.

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“…Similarly, the delocalized ptCcontaining molecules composed of C, B, H atoms were also extensively studied [14][15][16][17][18][19][20][21][22][23][24][25][26]. The smallest organic molecule C 3 B 2 H 4 with ptC, proposed by Minyaev et al [18], can be served as a basic block to build an extended system such as the stable beltlike compounds (C 3 B 2 ) n H 4 (n = 2-6) and tubular compounds (C 3 B 2 ) n [25,31].…”

Section: Introductionmentioning

confidence: 99%