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Sarmah K, Kalita AJ, Purkayastha SK, Guha AK. Pushing The Extreme of Multicentre Bonding: Planar Pentacoordinate Hydride. Angew Chem Int Ed Engl 2024; 63:e202318741. [PMID: 38298097 DOI: 10.1002/anie.202318741] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2023] [Revised: 01/05/2024] [Accepted: 01/31/2024] [Indexed: 02/02/2024]
Abstract
Planar hypercoordination has sparkled interest among the researchers from last few decades. Most of the elements in the Periodic Table have shown this remarkable structural feature. However, the smallest element, hydrogen, is missing in the list. No evidence is there in the literature. Herein, we introduce the first planar pentacoordinate hydrogen atom (ppH) in the global minimum geometry of Li5 H6 - cluster. Bonding analysis indicates that the central hydrogen atom is stabilized by multicentre bonding with five surrounding Li atoms. Natural charge analysis reveals that the central hydrogen is acting like a hydride which is strongly attracted by the positively charged surrounding lithium centres. The ppH structure is stabilized by strong electrostatic attraction as well as extensive multicentre bonding. Aromaticity has no role to play here. The cluster is dynamically stable and is expected to be detected in gas phase.
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Affiliation(s)
- Kangkan Sarmah
- Advanced Computational Chemistry Centre, Cotton University Panbazar, Guwahati, Assam, INDIA-, 781001
| | - Amlan J Kalita
- Advanced Computational Chemistry Centre, Cotton University Panbazar, Guwahati, Assam, INDIA-, 781001
| | - Siddhartha K Purkayastha
- Advanced Computational Chemistry Centre, Cotton University Panbazar, Guwahati, Assam, INDIA-, 781001
| | - Ankur K Guha
- Advanced Computational Chemistry Centre, Cotton University Panbazar, Guwahati, Assam, INDIA-, 781001
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Kalita AJ, Rohman SS, Sahu PP, Guha AK. Planar Tetracoordinate Hydrogen: Pushing the Limit of Multicentre Bonding. Angew Chem Int Ed Engl 2024; 63:e202317312. [PMID: 38010906 DOI: 10.1002/anie.202317312] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2023] [Revised: 11/22/2023] [Accepted: 11/24/2023] [Indexed: 11/29/2023]
Abstract
Among the list of planar tetracoordinate atoms, the smallest element hydrogen is missing. No experimental and theoretical evidence have ever been put forwarded. Herein, we introduce the first planar tetracoordinate hydrogen atom (ptH) in the global minimum geometry of In4 H+ cluster. Bonding analysis indicates that the central hydrogen atom is acting like a proton and significant charge transfer from the surrounding In4 framework results in a negative charge of the central hydrogen atom. The proposed global minimum geometry possesses σ-aromaticity and the central hydrogen atom forms unusual multicentre bond with more than three centres.
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Affiliation(s)
- Amlan J Kalita
- Advanced Computational Chemistry Centre, Cotton University Panbazar, Guwahati, Assam, 781001, India
| | - Shahnaz S Rohman
- Department of Chemistry, National Institute of Technology, Calicut, Kerala, 673601, India
| | - Prem P Sahu
- Department of Chemistry, Indian Institute of Technology Hyderabad Kandi, Sangareddy, Telangana, 502284, India
- Department of Chemistry "Ugo Schiff", University of Florence, Via della Lastruccia 3, 50019, Sesto Fiorentino, Italy
| | - Ankur Kanti Guha
- Advanced Computational Chemistry Centre, Cotton University Panbazar, Guwahati, Assam, 781001, India
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Abstract
Despite the long list of planar tetracoordinate atoms, hydrogen is elusive. This is especially due to the inherent ability of hydrogen to form multicenter bonds with other centers. Herein, we introduce the first planar tetracoordinate hydrogen atom (ptH) in the global minimum geometry of a C2v symmetric Li4H4- cluster. Bonding analysis indicates that the central hydrogen atom is stabilized by multicenter bonding with four surrounding Li atoms. Natural charge analysis reveals that the central hydrogen is acting like a hydride, which is strongly attracted by the positively charged surrounding lithium centers. The ptH structure is stabilized by strong electrostatic attraction as well as extensive multicenter bonding. Aromaticity has no role to play here. The cluster is dynamically stable and is expected to be detected in the gas phase. Introduction of a heavier alkali metal such as sodium makes the planar C2v cluster a local minimum with slightly higher energy than the linear global minimum geometry.
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Affiliation(s)
- Kangkan Sarmah
- Advanced Computational Chemistry Centre, Cotton University, Panbazar, Guwahati, Assam, India 781001
| | - Amlan Jyoti Kalita
- Advanced Computational Chemistry Centre, Cotton University, Panbazar, Guwahati, Assam, India 781001
| | - Ankur K Guha
- Advanced Computational Chemistry Centre, Cotton University, Panbazar, Guwahati, Assam, India 781001
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Gohain N, Bordoloi A, Kalita AJ, Guha AK. Rare Spin Avoided σ-σ Diradical Planar Tetracoordinate Boron Cluster: A Proto-Star for Planar Pentacoordination. Chemphyschem 2023; 24:e202300101. [PMID: 37409624 DOI: 10.1002/cphc.202300101] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2023] [Revised: 04/11/2023] [Accepted: 07/06/2023] [Indexed: 07/07/2023]
Abstract
We report a global planar star-like cluster B3 Li3 featuring three planar tetracoordinate boron centres with a rare spin avoided σ-σ diradical character. The cluster was found to be stable towards dissociation into different fragments. The spin density was found to be localized solely on the three boron atoms in the molecular plane. This spin avoided σ-σ diradical character leads to the extension of the coordination number to yield a neutral B3 Li3 H3 and a cationic B3 Li3 H3 + cluster with three planar pentacoordinate boron centres in their global minimum structures. The planar geometry of the aninonic B3 Li3 H3 - cluster is slightly higher in energy. The planar global clusters were found to maintain planarity in their ligand protected benzene bound complexes, B3 Li3 (Bz)3 , B3 Li3 H3 (Bz)3 and B3 Li3 H3 (Bz)3 + with high ligand dissociation energies offering candidature for experimental detection.
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Affiliation(s)
- Namrata Gohain
- Advanced Computational Chemistry Centre, Cotton University, Panbazar, Guwahati, Assam, INDIA-, 781001
| | - Abhik Bordoloi
- Advanced Computational Chemistry Centre, Cotton University, Panbazar, Guwahati, Assam, INDIA-, 781001
| | - Amlan J Kalita
- Advanced Computational Chemistry Centre, Cotton University, Panbazar, Guwahati, Assam, INDIA-, 781001
| | - Ankur K Guha
- Advanced Computational Chemistry Centre, Cotton University, Panbazar, Guwahati, Assam, INDIA-, 781001
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Wang MH, Kalita AJ, Orozco-Ic M, Yan GR, Chen C, Yan B, Castillo-Toraya G, Tiznado W, Guha AK, Pan S, Merino G, Cui ZH. Planar pentacoordinate s-block metals. Chem Sci 2023; 14:8785-8791. [PMID: 37621437 PMCID: PMC10445469 DOI: 10.1039/d2sc05939h] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2022] [Accepted: 07/14/2023] [Indexed: 08/26/2023] Open
Abstract
The presence of a delocalized π-bond is often considered an essential criterion for achieving planar hypercoordination. Herein, we show that σ-delocalization could be sufficient to make the planar configuration the most stable isomer in a series of planar pentacoordinate s-block metals. High-level ab initio computations reveal that the global minimum of a series of interalkali and interalkali-alkaline earth clusters (LiNa5, Li5Mg+, Na5Mg+, K5Ca+, CaRb5+, Rb5Sr+, and SrCs5+) adopts a singlet D5h structure with a planar pentacoordinate lithium or alkaline earth metal (AE = Mg, Ca, Sr). These clusters are unusual combinations to stabilize a planar pentacoordinate atom, as all their constituents are electropositive. Despite the absence of π-electrons, Hückel's rule is fulfilled by the six σ-electrons. Furthermore, the systems exhibit a diatropic ring current in response to an external magnetic field and a strong magnetic shielding, so they might be classified as σ-aromatic. Therefore, multicenter σ-bonds and the resulting σ-delocalization stabilize these clusters, even though they lack π-aromaticity.
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Affiliation(s)
- Meng-Hui Wang
- Institute of Atomic and Molecular Physics, Jilin University Changchun 130023 China
| | - Amlan J Kalita
- Advanced Computational Chemistry Centre, Department of Chemistry, Cotton University Panbazar Guwahati Assam 781001 India
| | - Mesías Orozco-Ic
- Donostia International Physics Center (DIPC) 20018 Donostia Euskadi Spain
| | - Gai-Ru Yan
- Institute of Atomic and Molecular Physics, Jilin University Changchun 130023 China
| | - Chen Chen
- Institute of Atomic and Molecular Physics, Jilin University Changchun 130023 China
| | - Bing Yan
- Institute of Atomic and Molecular Physics, Jilin University Changchun 130023 China
| | - Gabriela Castillo-Toraya
- Departamento de Física Aplicada, Centro de Investigación y de Estudios Avanzados Unidad Mérida. Km 6 Antigua Carretera a Progreso. Apdo. Postal 73, Cordemex 97310 Mérida Yucatan Mexico
| | - William Tiznado
- Centro de Química Teórica & Computacional (CQT&C), Departamento de Ciencias Químicas, Facultad de Ciencias Exactas, Universidad Andres Bello Avenida República 275 Santiago Chile
| | - Ankur K Guha
- Advanced Computational Chemistry Centre, Department of Chemistry, Cotton University Panbazar Guwahati Assam 781001 India
| | - Sudip Pan
- Institute of Atomic and Molecular Physics, Jilin University Changchun 130023 China
| | - Gabriel Merino
- Departamento de Física Aplicada, Centro de Investigación y de Estudios Avanzados Unidad Mérida. Km 6 Antigua Carretera a Progreso. Apdo. Postal 73, Cordemex 97310 Mérida Yucatan Mexico
| | - Zhong-Hua Cui
- Institute of Atomic and Molecular Physics, Jilin University Changchun 130023 China
- Key Laboratory of Physics and Technology for Advanced Batteries (Ministry of Education), Jilin University Changchun 130023 China
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σ-Aromaticity in planar pentacoordinate aluminium and gallium clusters. Sci Rep 2022; 12:10041. [PMID: 35710864 PMCID: PMC9203769 DOI: 10.1038/s41598-022-14430-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2022] [Accepted: 05/17/2022] [Indexed: 11/08/2022] Open
Abstract
Planar hypercoordinate structures are gaining immense attention due to the shift from common paradigm. Herein, our high level ab initio calculations predict that planar pentacoordinate aluminium and gallium centres in Cu5Al2+ and Cu5Ga2+ clusters are global minima in their singlet ground states. These clusters are thermodynamically and kinetically very stable. Detailed electronic structure analyses reveal the presence of σ-aromaticity which is the driving force for the stability of the planar form.
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Kalita AJ, Baruah I, Sarmah K, Borah RR, Yashmin F, Guha AK. Planar Pentacoordinate Zinc Group Elements Stabilized by Multicentric Bonds. Inorg Chem 2022; 61:1259-1263. [PMID: 35007083 DOI: 10.1021/acs.inorgchem.1c03426] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Planar pentacoordinate zinc group elements, (M = Zn, Cd, Hg) were computationally found to be at a global minimum in Li5M+ clusters. The stability of these clusters is due to the presence of multicentric bonds. The central element (Zn, Cd, Hg) in each cluster features a negative oxidation state owing to the in-plane electron donation by the Li5+ framework. A similar global minimum planar pentacoordinate structure is found in Na5Zn+ and Na5Cd+ clusters.
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Affiliation(s)
- Amlan J Kalita
- Advanced Computational Chemistry Centre, Department of Chemistry, Cotton University, Panbazar, Guwahati 781001, Assam, India
| | - Indrani Baruah
- Advanced Computational Chemistry Centre, Department of Chemistry, Cotton University, Panbazar, Guwahati 781001, Assam, India
| | - Kangkan Sarmah
- Advanced Computational Chemistry Centre, Department of Chemistry, Cotton University, Panbazar, Guwahati 781001, Assam, India
| | - Ritam R Borah
- Advanced Computational Chemistry Centre, Department of Chemistry, Cotton University, Panbazar, Guwahati 781001, Assam, India
| | - Farnaz Yashmin
- Advanced Computational Chemistry Centre, Department of Chemistry, Cotton University, Panbazar, Guwahati 781001, Assam, India
| | - Ankur K Guha
- Advanced Computational Chemistry Centre, Department of Chemistry, Cotton University, Panbazar, Guwahati 781001, Assam, India
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Wang MH, Chen C, Pan S, Cui ZH. Planar hexacoordinate gallium. Chem Sci 2021; 12:15067-15076. [PMID: 34909147 PMCID: PMC8612373 DOI: 10.1039/d1sc05089c] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2021] [Accepted: 10/26/2021] [Indexed: 11/21/2022] Open
Abstract
We report the first planar hexacoordinate gallium (phGa) center in the global minimum of the GaBe6Au6 + cluster which has a star-like D 6h geometry with 1A1g electronic state, possessing a central gallium atom encompassed by a Be6 hexagon and each Be-Be edge is further capped by an Au atom. The electronic delocalization resulting in double aromaticity (both σ and π) provides electronic stability in the planar form of the GaBe6Au6 + cluster. The high kinetic stability of the title cluster is also understood by Born-Oppenheimer molecular dynamics simulations. The energy decomposition analysis in combination with the 'natural orbitals for chemical valence' theory reveals that the bonding in the GaBe6Au6 + cluster is best expressed as the doublet Ga atom with 4s24p⊥ 1 electronic configuration forming an electron-sharing π bond with the doublet Be6Au6 + moiety followed by Ga(s)→[Be6Au6 +] σ-backdonation and two sets of Ga(p‖)←[Be6Au6 +] σ-donations.
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Affiliation(s)
- Meng-Hui Wang
- Institute of Atomic and Molecular Physics, Key Laboratory of Physics and Technology for Advanced Batteries (Ministry of Education), Jilin University Changchun China
| | - Chen Chen
- Institute of Atomic and Molecular Physics, Key Laboratory of Physics and Technology for Advanced Batteries (Ministry of Education), Jilin University Changchun China
| | - Sudip Pan
- Institute of Advanced Synthesis, School of Chemistry and Molecular Engineering, Jiangsu National Synergetic Innovation Center for Advanced Materials, Nanjing Tech University Nanjing China
- Fachbereich Chemie, Philipps-Universität Marburg Hans-Meerwein-Strasse 4 35032 Marburg Germany
| | - Zhong-Hua Cui
- Institute of Atomic and Molecular Physics, Key Laboratory of Physics and Technology for Advanced Batteries (Ministry of Education), Jilin University Changchun China
- Beijing National Laboratory for Molecular Sciences China
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Abstract
Six-valence-electron planar pentacoordinate beryllium (ppBe) is explored herein as a global minimum, which is only constructed by s-block metals in BeM5+ (M = Cu, Ag, Au). The bonding in ppBe can be regarded as the excited-stated Be with a 2px12py1 electronic configuration, forming electron sharing with doublet M5+ motifs followed by two sets of Be(p∥) → [M5+] σ donations and one Be(s) ← [M5+] σ back-donation. Thus, the σ aromaticity originating from three delocalized σ orbitals gives rise to the whole stability of the high D5h-symmetry ppBe and strongly enriches s-block planar hypercoordinate bonding.
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Affiliation(s)
- Chen Chen
- Institute of Atomic and Molecular Physics, Key Laboratory of Physics and Technology for Advanced Batteries (Ministry of Education), Jilin University, Changchun 130012, China
| | - Yu-Qian Liu
- Institute of Atomic and Molecular Physics, Key Laboratory of Physics and Technology for Advanced Batteries (Ministry of Education), Jilin University, Changchun 130012, China
| | - Zhong-Hua Cui
- Institute of Atomic and Molecular Physics, Key Laboratory of Physics and Technology for Advanced Batteries (Ministry of Education), Jilin University, Changchun 130012, China
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Abstract
We have explored the chemical space of BAl4Mg−/0/+ for the first time and theoretically characterized several isomers with interesting bonding patterns. We have used chemical intuition and a cluster building method based on the tabu-search algorithm implemented in the Python program for aggregation and reaction (PyAR) to obtain the maximum number of possible stationary points. The global minimum geometries for the anion (1a) and cation (1c) contain a planar tetracoordinate boron (ptB) atom, whereas the global minimum geometry for the neutral (1n) exhibits a planar pentacoordinate boron (ppB) atom. The low-lying isomers of the anion (2a) and cation (3c) also contain a ppB atom. The low-lying isomer of the neutral (2n) exhibits a ptB atom. Ab initio molecular dynamics simulations carried out at 298 K for 2000 fs suggest that all isomers are kinetically stable, except the cation 3c. Simulations carried out at low temperatures (100 and 200 K) for 2000 fs predict that even 3c is kinetically stable, which contains a ppB atom. Various bonding analyses (NBO, AdNDP, AIM, etc.) are carried out for these six different geometries of BAl4Mg−/0/+ to understand the bonding patterns. Based on these results, we conclude that ptB/ppB scenarios are prevalent in these systems. Compared to the carbon counter-part, CAl4Mg−, here the anion (BAl4Mg−) obeys the 18 valence electron rule, as B has one electron fewer than C. However, the neutral and cation species break the rule with 17 and 16 valence electrons, respectively. The electron affinity (EA) of BAl4Mg is slightly higher (2.15 eV) than the electron affinity of CAl4Mg (2.05 eV). Based on the EA value, it is believed that these molecules can be identified in the gas phase. All the ptB/ppB isomers exhibit π/σ double aromaticity. Energy decomposition analysis predicts that the interaction between BAl4−/0/+ and Mg is ionic in all these six systems.
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Abstract
Isomers of CAl4Mg and CAl4Mg− have been theoretically characterized for the first time. The most stable isomer for both the neutral and anion contain a planar tetracoordinate carbon (ptC) atom. Unlike the isovalent CAl4Be case, which contains a planar pentacoordinate carbon atom as the global minimum geometry, replacing beryllium with magnesium makes the ptC isomer the global minimum due to increased ionic radii of magnesium. However, it is relatively easier to conduct experimental studies for CAl4Mg0/− as beryllium is toxic. While the neutral molecule containing the ptC atom follows the 18 valence electron rule, the anion breaks the rule with 19 valence electrons. The electron affinity of CAl4Mg is in the range of 1.96–2.05 eV. Both the global minima exhibit π/σ double aromaticity. Ab initio molecular dynamics simulations were carried out for both the global minima at 298 K for 10 ps to confirm their kinetic stability.
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