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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http://dx.doi.org/10.1002/anie.201410407 | DOI Listing |
J Comput Chem
January 2025
Department of Chemistry, Birla Institute of Technology Mesra, Ranchi, Jharkhand, India.
In this study, we investigated the potential energy surface of BXY (X = B, Al, Ga; Y = C, Si, Ge) clusters employing a few global optimization techniques. Remarkably, the global minimum structure obtained for most of the cases revealed a planar tetracoordinate boron atom, shedding light on the inherent stability of this motif. A comparative analysis of the performance of the different global optimization techniques employed is presented, offering insights into their efficacy.
View Article and Find Full Text PDFChemistry
November 2024
Department of Chemistry, Xinzhou Normal University, Xinzhou, Shanxi, 034000, China.
Angew Chem Int Ed Engl
November 2024
Institute of Atomic and Molecular Physics, Jilin University, Changchun, 130023, China.
Planar hypercoordinate motifs represent an intriguing frontier in chemistry, challenging traditional bonding norms. As electronegativity of the central atom increases, achieving planar hypercoordination becomes more difficult due to restricted delocalization, making the design of planar hypercoordinate halogens particularly puzzling. Here, we conduct an extensive computational survey of LiX (n=4, 5, 6; X=F, Cl, Br, I) clusters, revealing a starlike D-symmetry global minimum in LiX (X=F, Cl, Br) with a planar pentacoordinate halogen (ppX), where X is located at the center of LiX crown.
View Article and Find Full Text PDFAngew Chem Int Ed Engl
October 2024
Institute of Atomic and Molecular Physics, Jilin University, Changchun, 130023, China.
Photoelectron spectroscopy and theoretical calculations have identified the global minimum structure of the 16-valence electron SiCu cluster, which features a planar tetracoordinate silicon (ptSi) in a rhombic arrangement. The Si and Cu triangles are interconnected by a Si/Cu edge, forming an ordered chain-like structure. Besides the conventional 2c-2e σ-bond connecting Si and Cu, the stability of this cluster is reinforced by a delocalized 3c-2e σ-bond in Cu and a π-bond in Si.
View Article and Find Full Text PDFInorg Chem
July 2024
Institute of Atomic and Molecular Physics, Jilin University, Changchun 130023, China.
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