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Recio P, Alessandrini S, Vanuzzo G, Pannacci G, Baggioli A, Marchione D, Caracciolo A, Murray VJ, Casavecchia P, Balucani N, Cavallotti C, Puzzarini C, Barone V. Intersystem crossing in the entrance channel of the reaction of O( 3P) with pyridine. Nat Chem 2022; 14:1405-1412. [PMID: 36175514 DOI: 10.1038/s41557-022-01047-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2021] [Accepted: 08/25/2022] [Indexed: 01/04/2023]
Abstract
Two quantum effects can enable reactions to take place at energies below the barrier separating reactants from products: tunnelling and intersystem crossing between coupled potential energy surfaces. Here we show that intersystem crossing in the region between the pre-reactive complex and the reaction barrier can control the rate of bimolecular reactions for weakly coupled potential energy surfaces, even in the absence of heavy atoms. For O(3P) plus pyridine, a reaction relevant to combustion, astrochemistry and biochemistry, crossed-beam experiments indicate that the dominant products are pyrrole and CO, obtained through a spin-forbidden ring-contraction mechanism. The experimental findings are interpreted-by high-level quantum-chemical calculations and statistical non-adiabatic computations of branching fractions-in terms of an efficient intersystem crossing occurring before the high entrance barrier for O-atom addition to the N-atom lone pair. At low to moderate temperatures, the computed reaction rates prove to be dominated by intersystem crossing.
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Affiliation(s)
- Pedro Recio
- Dipartimento di Chimica, Biologia e Biotecnologie, Università degli Studi di Perugia, Perugia, Italy
| | - Silvia Alessandrini
- Scuola Normale Superiore, Pisa, Italy
- Dipartimento di Chimica 'Giacomo Ciamician', University of Bologna, Bologna, Italy
| | - Gianmarco Vanuzzo
- Dipartimento di Chimica, Biologia e Biotecnologie, Università degli Studi di Perugia, Perugia, Italy
| | - Giacomo Pannacci
- Dipartimento di Chimica, Biologia e Biotecnologie, Università degli Studi di Perugia, Perugia, Italy
| | - Alberto Baggioli
- Dipartimento di Chimica, Materiali e Ingegneria Chimica 'Giulio Natta', Politecnico di Milano, Milan, Italy
| | - Demian Marchione
- Dipartimento di Chimica, Biologia e Biotecnologie, Università degli Studi di Perugia, Perugia, Italy
| | - Adriana Caracciolo
- Dipartimento di Chimica, Biologia e Biotecnologie, Università degli Studi di Perugia, Perugia, Italy
- Department of Aerospace Engineering Sciences, University of Colorado, Boulder, CO, USA
| | - Vanessa J Murray
- Dipartimento di Chimica, Biologia e Biotecnologie, Università degli Studi di Perugia, Perugia, Italy
- Montana State University, Bozeman, MT, USA
| | - Piergiorgio Casavecchia
- Dipartimento di Chimica, Biologia e Biotecnologie, Università degli Studi di Perugia, Perugia, Italy
| | - Nadia Balucani
- Dipartimento di Chimica, Biologia e Biotecnologie, Università degli Studi di Perugia, Perugia, Italy.
| | - Carlo Cavallotti
- Dipartimento di Chimica, Materiali e Ingegneria Chimica 'Giulio Natta', Politecnico di Milano, Milan, Italy.
| | - Cristina Puzzarini
- Dipartimento di Chimica 'Giacomo Ciamician', University of Bologna, Bologna, Italy.
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Yang Z, He C, Goettl SJ, Paul D, Kaiser RI, Silva MX, Galvão BRL. Gas-Phase Preparation of Silyl Cyanide (SiH 3CN) via a Radical Substitution Mechanism. J Am Chem Soc 2022; 144:8649-8657. [PMID: 35504731 DOI: 10.1021/jacs.2c01349] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The silyl cyanide (SiH3CN) molecule, the simplest representative of a fully saturated silacyanide, was prepared in the gas phase under single-collision conditions via a radical substitution mechanism. The chemical dynamics were direct and revealed a pronounced backward scattering as a consequence of a transition state with a pentacoordinated silicon atom and almost colinear geometry of the attacking cyano radical and leaving hydrogen. Compared to the isovalent cyano (CN)-methane (CH4) system, the CN-SiH4 system dramatically reduces the energy of the transition state to silyl cyanide by nearly 100 kJ mol-1, which reveals a profound effect on the chemical bonding and reaction mechanism. In extreme high-temperature environments including circumstellar envelopes of IRC +10216, this versatile radical substitution mechanism may synthesize organosilicon molecules via reactions of silane with doublet radicals. Overall, this study provides rare insights into the exotic reaction mechanisms of main-group XIV elements in extreme environments and affords deeper insights into fundamental molecular mass growth processes involving silicon in our universe.
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Affiliation(s)
- Zhenghai Yang
- Department of Chemistry, University of Hawai'i at Manoa, Honolulu, Hawaii 96822, United States
| | - Chao He
- Department of Chemistry, University of Hawai'i at Manoa, Honolulu, Hawaii 96822, United States
| | - Shane J Goettl
- Department of Chemistry, University of Hawai'i at Manoa, Honolulu, Hawaii 96822, United States
| | - Dababrata Paul
- Department of Chemistry, University of Hawai'i at Manoa, Honolulu, Hawaii 96822, United States
| | - Ralf I Kaiser
- Department of Chemistry, University of Hawai'i at Manoa, Honolulu, Hawaii 96822, United States
| | - Mateus X Silva
- Centro Federal de Educação Tecnológica de Minas Gerais, CEFET-MG, Avenue Amazonas 5253, 30421-169 Belo Horizonte, Minas Gerais, Brazil
| | - Breno R L Galvão
- Centro Federal de Educação Tecnológica de Minas Gerais, CEFET-MG, Avenue Amazonas 5253, 30421-169 Belo Horizonte, Minas Gerais, Brazil
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He Y, Dai C, Wang D, Zhu J, Tan G. Phosphine-Stabilized Germylidenylpnictinidenes as Synthetic Equivalents of Heavier Nitrile and Isocyanide in Cycloaddition Reactions with Alkynes. J Am Chem Soc 2022; 144:5126-5135. [PMID: 35263091 DOI: 10.1021/jacs.2c00305] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
The reactions of chlorogermylene MsFluindtBu-GeCl 1, supported by a sterically encumbered hydrindacene ligand MsFluindtBu, with NaPCO(dioxane)2.5 and NaAsCO(18-c-6) in the presence of trimethylphosphine afforded trimethylphosphine-stabilized germylidenyl-phosphinidene 2 and -arsinidene 3, respectively. Structural and computational investigations reveal that the Ge-E' bond (E' = P and As) features a multiple-bond character. 2 and 3 exhibit diverse reactivity toward trimethylsilylacetylene and 4-tetrabutylphenylacetylene. Specifically, 2 underwent cycloadditions with both alkynes affording the first six-membered aromatic phosphagermabenzen-1-ylidenes 4 and 5, respectively, through the heavier isocyanide intermediate MsFluindtBu-PGe. In contrast, 3 could serve as a synthetic equivalent of heavier isocyanides and nitriles when treated with trimethylsilylacetylene and 4-tetrabutylphenylacetylene yielding arsagermene 6 and arsolylgermylene 7, respectively. The reaction mechanisms for the cycloadditions were investigated through density functional theory calculations. The reactivity studies highlight the potential of 2 and 3 in accessing heavy main-group element-containing heterocycles.
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Affiliation(s)
- Yuhao He
- College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123, China
| | - Chenshu Dai
- State Key Laboratory of Physical Chemistry of Solid Surfaces, Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry, Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China
| | - Dongmin Wang
- College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123, China
| | - Jun Zhu
- State Key Laboratory of Physical Chemistry of Solid Surfaces, Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry, Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China
| | - Gengwen Tan
- College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123, China
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He C, Goettl SJ, Yang Z, Doddipatla S, Kaiser RI, Silva MX, Galvão BRL. Directed gas-phase preparation of the elusive phosphinosilylidyne (SiPH 2, X 2A'') and cis/trans phosphinidenesilyl (HSiPH; X 2A') radicals under single-collision conditions. Phys Chem Chem Phys 2021; 23:18506-18516. [PMID: 34612389 DOI: 10.1039/d1cp02812j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The reaction of the D1-silylidyne radical (SiD; X2Π) with phosphine (PH3; X1A1) was conducted in a crossed molecular beams machine under single collision conditions. Merging of the experimental results with ab initio electronic structure and statistical Rice-Ramsperger-Kassel-Marcus (RRKM) calculations indicates that the reaction is initiated by the barrierless formation of a van der Waals complex (i0) as well as intermediate (i1) formed via the barrierless addition of the SiD radical with its silicon atom to the non-bonding electron pair of phosphorus of the phosphine. Hydrogen shifts from the phosphorous atom to the adjacent silicon atom yield intermediates i2a, i2b, i3; unimolecular decomposition of these intermediates leads eventually to the formation of trans/cis-phosphinidenesilyl (HSiPH, p2/p4) and phosphinosilylidyne (SiPH2, p3) via hydrogen deuteride (HD) loss (experiment: 80 ± 11%, RRKM: 68.7%) and d-trans/cis-phosphinidenesilyl (DSiPH, p2'/p4') plus molecular hydrogen (H2) (experiment: 20 ± 7%, RRKM: 31.3%) through indirect scattering dynamics via tight exit transition states. Overall, the study reveals branching ratios of p2/p4/p2'/p4' (trans/cis HSiPH/DSiPH) to p3 (SiPH2) of close to 4 : 1. The present study sheds light on the complex reaction dynamics of the silicon and phosphorous systems involving multiple atomic hydrogen migrations and tight exit transition states, thus opening up a versatile path to access the previously elusive phosphinidenesilyl and phosphinosilylidyne doublet radicals, which represent potential targets of future astronomical searches toward cold molecular clouds (TMC-1), star forming regions (Sgr(B2)), and circumstellar envelopes of carbon rich stars (IRC + 10216).
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Affiliation(s)
- Chao He
- Department of Chemistry, University of Hawai'i at Manoa, Honolulu, Hawaii 96822, USA.
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