Dataset Information

Formation and Reactivity of a Hexahydridosilicate [SiH₆ ]^2- Coordinated by a Macrocycle-Supported Strontium Cation.

ABSTRACT: The cationic benzyl complex [(Me₄ TACD)Sr(CH₂ Ph)][A] (Me₄ TACD=1,4,7,10-tetramethyltetraazacyclododecane; A=B(C₆ H₃ -3,5-Me₂ )₄ ) reacted with two equivalents of phenylsilane to give the bridging hexahydridosilicate complex [(Me₄ TACD)₂ Sr₂ (thf)₄ (μ-κ³ : κ³ -SiH₆ )][A]₂ (3 a). Rapid phenyl exchange between phenylsilane molecules is assumed to generate monosilane SiH₄ that is trapped by two strontium hydride cations [(Me₄ TACD)SrH(thf)_x ]⁺ . Complex 3 a decomposed in THF at room temperature to give the terminal silanide complex [(Me₄ TACD)Sr(SiH₃ )(thf)₂ ][A], with release of H₂ . Upon reaction with a weak Brønsted acid, CO₂ , and 1,3,5,7-cyclooctatetraene SiH₄ was released. The reaction of a 1 : 2 mixture of cationic benzyl and neutral dibenzyl complex with phenylsilane gave the trinuclear silanide complex [(Me₄ TACD)₃ Sr₃ (μ₂ -H)₃ (μ₃ -SiH₃ )₂ ][A], while ⁿ OctSiH₃ led to the trinuclear (n-octyl)pentahydridosilicate complex [(Me₄ TACD)₃ Sr₃ (μ₂ -H)₃ (μ₃ -SiH₅ ⁿ Oct)][A].

SUBMITTER: Hollerhage T

PROVIDER: S-EPMC9303417 | biostudies-literature | 2022 Mar

REPOSITORIES: biostudies-literature

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Publications

Formation and Reactivity of a Hexahydridosilicate [SiH6 ]2- Coordinated by a Macrocycle-Supported Strontium Cation.

Höllerhage Thomas T Ghana Priyabrata P Spaniol Thomas P TP Carpentier Ambre A Maron Laurent L Englert Ulli U Okuda Jun J

Angewandte Chemie (International ed. in English) 20220114 10

The cationic benzyl complex [(Me4 TACD)Sr(CH2 Ph)][A] (Me4 TACD=1,4,7,10-tetramethyltetraazacyclododecane; A=B(C6 H3 -3,5-Me2 )4 ) reacted with two equivalents of phenylsilane to give the bridging hexahydridosilicate complex [(Me4 TACD)2 Sr2 (thf)4 (μ-κ3 : κ3 -SiH6 )][A]2 (3 a). Rapid phenyl exchange between phenylsilane molecules i ...[more]

PMID: 34874085

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Project description:The gas-phase reaction between the ethyl cation (C2H5+) and ethyne (C2H2) is re-investigated by measuring absolute reactive cross sections (CSs) and branching ratios (BRs) as a function of collision energy, in the thermal and hyperthermal energy range, via tandem-guided ion beam mass spectrometry under single collision conditions. Dissociative photoionization of C2H5Br using tuneable VUV radiation in the range 10.5-14.0 eV is employed to generate C2H5+, which has also allowed us to explore the impact of increasing (vibrational) excitation on the reactivity. Reactivity experiments are complemented by theoretical calculations, at the G4 level of theory, of the relative energies and structures of the most relevant stationary points on the reactive potential energy hypersurface (PES) and by mass-analyzed ion kinetic energy (MIKE) spectrometry experiments to probe the metastable decomposition from the [C4H7]+ PES and elucidate the underlying reaction mechanisms. Two main product channels have been identified at a centre-of-mass collision energy of ∼0.1 eV: (a) C3H3++CH4, with BR = 0.76±0.05 and (b) C4H5++H2, with BR = 0.22±0.02. A third channel giving C2H3+ in association with C2H4 is shown to emerge at both high internal excitation of C2H5+ and high collision energies. From CS measurements, energy-dependent total rate constants in the range 4.3×10-11-5.2×10-10 cm3·molecule-1·s-1 have been obtained. Theoretical calculations indicate that both channels stem from a common covalently bound intermediate, CH3CH2CHCH+, from which barrierless and exothermic pathways exist for the production of both cyclic c-C3H3+ and linear H2CCCH+ isomers of the main product channel. For the minor C4H5+ product, two isomers are energetically accessible: the three-member cyclic isomer c-C3H2(CH3)+ and the higher energy linear structure CH2CHCCH2+, but their formation requires multiple isomerization steps and passages via transition states lying only 0.11 eV below the reagents' energy, thus explaining the smaller BR. Results have implications for the modeling of hydrocarbon chemistry in the interstellar medium and the atmospheres of planets and satellites as well as in laboratory plasmas (e.g., plasma-enhanced chemical vapor deposition of carbon nanotubes and diamond-like carbon films).

Dataset Information

Formation and Reactivity of a Hexahydridosilicate [SiH₆ ]^2- Coordinated by a Macrocycle-Supported Strontium Cation.

Publications

Formation and Reactivity of a Hexahydridosilicate [SiH<sub>6</sub> ]<sup>2-</sup> Coordinated by a Macrocycle-Supported Strontium Cation.

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