Planar pentacoordinate carbon in [XC7H2]2+ (X = Be and Mg) and its derivatives

Pratik Sarkar; Krishnan Thirumoorthy; Anakuthil Anoop; Venkatesan S Thimmakondu

doi:10.1039/d2cp03299f

Planar pentacoordinate carbon in [XC₇H₂]²⁺ (X = Be and Mg) and its derivatives

Phys Chem Chem Phys. 2022 Nov 23;24(45):27606-27611. doi: 10.1039/d2cp03299f.

Authors

Pratik Sarkar¹, Krishnan Thirumoorthy², Anakuthil Anoop¹, Venkatesan S Thimmakondu³

Affiliations

¹ Department of Chemistry, Department of Chemistry, Indian Institute of Technology Kharagpur, Kharagpur-721 302, India. anoop@chem.iitkgp.ac.in.
² Department of Chemistry, School of Advanced Sciences, Vellore Institute of Technology, Vellore-632 014, Tamil Nadu, India.
³ Department of Chemistry and Biochemistry, San Diego State University, San Diego, CA 92182-1030, USA. vthimmakondusamy@sdsu.edu.

PMID: 36366951
DOI: 10.1039/d2cp03299f

Abstract

The planar pentacoordinate carbon (ppC) atom is theoretically established here in [XC₇H₂]²⁺ and [XSi₂C₅H₂]²⁺, where X = Be and Mg, using density functional theory. Inclusion compounds with alkali and alkaline earth metal ions are identified with the monomer units of tricyclic C₇H₂ and Si₂C₅H₂ isomers with a planar tetracoordinate carbon (ptC) atom. While all alkali and some alkaline earth metals (Ca²⁺, Sr²⁺, and Ba²⁺) stabilize the ptC isomer in both cases, Be²⁺ and Mg²⁺ ions form a bond directly with the ptC atom, thus making it a ppC atom. The theoretical binding energies computed at the PBE0-D3/def2-TZVP level of theory are ∼-9.68, -10.42, -5.85, and -5.47 eV for [BeC₇H₂]²⁺, [BeSi₂C₅H₂]²⁺, [MgC₇H₂]²⁺, and [MgSi₂C₅H₂]²⁺, respectively.