title: Four Decades of the Chemistry of Planar Hypercoordinate Compounds.
abstract: 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.
authors.affiliation: Center for Computational Quantum Chemistry, Department of Chemistry, University of Georgia, Athens, GA 30602-2525 (USA). lmyang.uio@gmail.com.|Present address: Hanse-Wissenschafts-Kolleg (Institute for Advanced Study), Lehmkuhlenbusch 4, 27753 Delmenhorst (Germany). lmyang.uio@gmail.com.|Bremen Center for Computational Materials Science, University of Bremen, Am Falturm 1, 28359, Bremen (Germany). lmyang.uio@gmail.com.
authors.forename: Li-Ming
authors.initials: LM
authors.lastname: Yang
authors.affiliation: Department of Physics, University of Minnesota, 116 Church St. SE, Minneapolis, MN 55416 (USA).
authors.forename: Eric
authors.initials: E
authors.lastname: Ganz
authors.affiliation: Department of Chemistry, Institute for Functional Nanomaterials, University of Puerto Rico, Rio Piedras Campus, San Juan, PR 00931 (USA). zhongfangchen@gmail.com.
authors.forename: Zhongfang
authors.initials: Z
authors.lastname: Chen
authors.affiliation: School of Chemistry and Chemical Engineering, University of the Chinese Academy of Sciences, Beijing, 100049 (China).
authors.forename: Zhi-Xiang
authors.initials: ZX
authors.lastname: Wang
authors.affiliation: Center for Computational Quantum Chemistry, Department of Chemistry, University of Georgia, Athens, GA 30602-2525 (USA).
authors.forename: Paul von Ragué
authors.initials: Pv
authors.lastname: Schleyer
keywords: Hypercoordination; coordination numbers; nonclassical molecules; planar coordination; theoretical chemistry