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Paul D, Sun BJ, He C, Yang Z, Goettl SJ, Yang T, Zhang BY, Chang AHH, Kaiser RI. Competing Si 2CH 4-H 2 and SiCH 2-SiH 4 Channels in the Bimolecular Reaction of Ground-State Atomic Carbon (C( 3P j)) with Disilane (Si 2H 6, X 1A 1g) under Single Collision Conditions. J Phys Chem A 2023; 127:1901-1908. [PMID: 36790335 DOI: 10.1021/acs.jpca.2c08417] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/16/2023]
Abstract
The bimolecular gas-phase reaction of ground-state atomic carbon (C(3Pj)) with disilane (Si2H6, X1A1g) was explored under single-collision conditions in a crossed molecular beam machine at a collision energy of 36.6 ± 4.5 kJ mol-1. Two channels were observed: a molecular hydrogen elimination plus Si2CH4 (reaction 1) pathway and a silane loss channel along with the formation of SiCH2 (reaction 2), with branching ratios of 20 ± 3 and 80 ± 4%, respectively. Both channels involved indirect scattering dynamics via long-lived Si2CH6 reaction intermediate(s); the latter eject molecular hydrogen and silane in "molecular" elimination channels within the rotational plane of the fragmenting intermediate nearly perpendicularly to the total angular momentum vector. These molecular elimination channels are associated with tight exit transition states as reflected in a significant electron rearrangement as visible from the chemical bonding in the light reaction products molecular hydrogen and silane. Once these hydrogenated silicon-carbide clusters are formed within the inner envelope of carbon stars such as of IRC + 10216, the stellar wind can drive both Si2CH4 and SiCH2 to the outside sections of the envelope, where they can be photolyzed. This is of particular importance to unravel potential formation pathways to disilicon monocarbide (Si2C) observed recently in the circumstellar shell of IRC + 10216.
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Affiliation(s)
- Dababrata Paul
- Department of Chemistry, University of Hawai'i at Manoa, Honolulu, Hawaii 96822, United States
| | - Bing-Jian Sun
- Department of Chemistry, National Dong Hwa University, Shoufeng, Hualien 974, Taiwan
| | - Chao He
- Department of Chemistry, University of Hawai'i at Manoa, Honolulu, Hawaii 96822, United States
| | - Zhenghai Yang
- 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
| | - Tao Yang
- Department of Chemistry, University of Hawai'i at Manoa, Honolulu, Hawaii 96822, United States
| | - Bo-Yu Zhang
- Department of Chemistry, National Dong Hwa University, Shoufeng, Hualien 974, Taiwan
| | - Agnes H H Chang
- Department of Chemistry, National Dong Hwa University, Shoufeng, Hualien 974, Taiwan
| | - Ralf I Kaiser
- Department of Chemistry, University of Hawai'i at Manoa, Honolulu, Hawaii 96822, United States
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Yang Z, Sun BJ, He C, Li JQ, Chang AHH, Kaiser RI. Gas-Phase Preparation of 1-Germavinylidene (H 2CGe; X 1A 1), the Isovalent Counterpart of Vinylidene (H 2CC; X 1A 1), via Non-adiabatic Dynamics through the Elementary Reaction of Ground State Atomic Carbon (C; 3P) with Germane (GeH 4; X 1A 1). J Phys Chem Lett 2023; 14:430-436. [PMID: 36622768 DOI: 10.1021/acs.jpclett.2c03749] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
1-Germavinylidene (H2CGe; X1A1), the germanium analogue of vinylidene (H2CC; X1A1), was prepared via a directed gas-phase synthesis through the bimolecular reaction of ground state atomic carbon (C; 3P) with germane (GeH4; X1A1) under single-collision conditions. The reaction commences with the barrierless insertion of carbon into the Ge-H bond followed by intersystem crossing from the triplet to singlet surface and migration of atomic hydrogen to germylene (H2GeCH2), which predominantly decomposes via molecular hydrogen loss to 1-germavinylidene (H2CGe; X1A1). Therefore, the replacement of a single carbon atom in the acetylene-vinylidene system by germanium critically impacts the chemical bonding, molecular structure, and thermodynamic stability of the carbene-type structures favoring 1-germavinylidene (H2CGe) over germyne (HGeCH) by 160 kJ mol-1. Hence, the carbon-germane system represents a benchmark in the exploration of the chemistries of main group 14 elements with germanium-bearing systems showing few similarities with the isovalent carbon system.
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Affiliation(s)
- Zhenghai Yang
- Department of Chemistry, University of Hawai'i at Manoa, Honolulu, Hawaii 96822, United States
| | - Bing-Jian Sun
- Department of Chemistry, National Dong Hwa University, Shoufeng, Hualien 974, Taiwan
| | - Chao He
- Department of Chemistry, University of Hawai'i at Manoa, Honolulu, Hawaii 96822, United States
| | - Jin-Qi Li
- Department of Chemistry, National Dong Hwa University, Shoufeng, Hualien 974, Taiwan
| | - Agnes H H Chang
- Department of Chemistry, National Dong Hwa University, Shoufeng, Hualien 974, Taiwan
| | - Ralf I Kaiser
- Department of Chemistry, University of Hawai'i at Manoa, Honolulu, Hawaii 96822, United States
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He C, Thomas AM, Dangi BB, Yang T, Kaiser RI, Lee HC, Sun BJ, Chang AHH. Formation of the Elusive Silylenemethyl Radical (HCSiH 2; X 2B 2) via the Unimolecular Decomposition of Triplet Silaethylene (H 2CSiH 2; a 3A″). J Phys Chem A 2022; 126:3347-3357. [PMID: 35584043 DOI: 10.1021/acs.jpca.2c01853] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We investigated the formation of small organosilicon molecules─potential precursors to silicon-carbide dust grains ejected by dying carbon-rich asymptotic giant branch stars─in the gas phase via the reaction of atomic carbon (C) in its 3P electronic ground state with silane (SiH4; X1A1) using the crossed molecular beams technique. The reactants collided under single collision conditions at a collision energy of 13.0 ± 0.2 kJ mol-1, leading to the formation of the silylenemethyl radical (HCSiH2; X2B2) via the unimolecular decomposition of triplet silaethylene (H2CSiH2; a3A″). The silaethylene radical was formed via hydrogen migration of the triplet silylmethylene (HCSiH3; X3A″) radical, which in turn was identified as the initial collision complex accessed via the barrierless insertion of atomic carbon into the silicon-hydrogen bond of silane. Our results mark the first observation of the silylenemethyl radical, where previously only its thermodynamically more stable methylsilylidyne (CH3Si; X2A″) and methylenesilyl (CH2SiH; X2A') isomers were observed in low-temperature matrices. Considering the abundance of silane and the availability of atomic carbon in carbon-rich circumstellar environments, our results suggest that future astrochemical models should be updated to include contributions from small saturated organosilicon molecules as potential precursors to pure gaseous silicon-carbides and ultimately to silicon-carbide dust.
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Affiliation(s)
- Chao He
- Department of Chemistry, University of Hawai'i at Manoa, Honolulu, Hawaii 96822, United States
| | - Aaron M Thomas
- Department of Chemistry, University of Hawai'i at Manoa, Honolulu, Hawaii 96822, United States
| | - Beni B Dangi
- Department of Chemistry, University of Hawai'i at Manoa, Honolulu, Hawaii 96822, United States
| | - Tao Yang
- 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
| | - Huan-Cheng Lee
- Department of Chemistry, National Dong Hwa University, Shoufeng, Hualien 974, Taiwan
| | - Bing-Jian Sun
- Department of Chemistry, National Dong Hwa University, Shoufeng, Hualien 974, Taiwan
| | - Agnes H H Chang
- Department of Chemistry, National Dong Hwa University, Shoufeng, Hualien 974, Taiwan
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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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