Infrared spectroscopic detection of the methylgermyl (H2GeCH3) radical and its perdeuterated counterpart in low temperature matrices

Doddipatla

et al. 2020

Chemistry A European J

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The silene molecule (H2SiCH2; X1A1) has been synthesized under single collision conditions via the bimolecular gas phase reaction of ground state methylidyne radicals (CH) with silane (SiH4). Exploiting crossed molecular beams experiments augmented by high‐level electronic structure calculations, the elementary reaction commenced on the doublet surface through a barrierless insertion of the methylidyne radical into a silicon‐hydrogen bond forming the silylmethyl (CH2SiH3; X2A′) complex followed by hydrogen migration to the methylsilyl radical (SiH2CH3; X2A′). Both silylmethyl and methylsilyl intermediates undergo unimolecular hydrogen loss to silene (H2SiCH2; X1A1). The exploration of the elementary reaction of methylidyne with silane delivers a unique view at the widely uncharted reaction dynamics and isomerization processes of the carbon–silicon system in the gas phase, which are noticeably different from those of the isovalent carbon system thus contributing to our knowledge on carbon silicon bond couplings at the molecular level.

Section: Methodssupporting

confidence: 88%

Directed Gas Phase Formation of Silene (H₂SiCH₂)

Doddipatla

et al. 2020

Chemistry A European J

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“…The methylgermyl radical represents the global minimum of the GeCH 5 PES. The energy difference between i1 and i2 of 72 kJ mol À 1 along with the barrier to isomerization of 151 kJ mol À 1 correlate nicely with earlier computational studies by Osamura et al (60-69 kJ mol À 1 ) [17] and Kudo and Nagase (151-160 kJ mol À 1 ). [22] The methylgermyl radical (GeH 2 CH 3 ; X 2 A'; i2) was found to undergo unimolecular decomposition via atomic hydrogen loss from the GeH 2 moiety via a lose exit transition state leading to the experimentally observed singlet methylgermylene (HGeCH 3 ; X 1 A'; p1) product.…”

supporting

confidence: 88%

“…Gas-phase kinetics of the reactions of germylenes have been studied [15] and methylgermylene (HGeCH 3 ; 8; X 1 A') was first tentatively characterized via laser flash photolysis of 1,3,4-trimethylgermacyclopent-3-ene; the UV spectrum and rate constants of its reactions with 10 different substrates were measured. [16] In 2010, HGeCH 3 was inferred from matrix isolation studies [17] via the ν 3 and ν 5 modes at 1803 and 1230 cm À 1 . Electronic structure calculations predicted the existence of three structural isomers.…”

mentioning

confidence: 99%

Gas Phase Formation of Methylgermylene (HGeCH3)

Doddipatla

et al. 2020

ChemPhysChem

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The methylgermylene species (HGeCH3; X1A′) has been synthesized via the bimolecular gas phase reaction of ground state methylidyne radicals (CH) with germane (GeH4) under single collision conditions in crossed molecular beams experiments. Augmented by electronic structure calculations, this elementary reaction was found to proceed through barrierless insertion of the methylidyne radical in one of the four germanium‐hydrogen bonds on the doublet potential energy surface yielding the germylmethyl (CH2GeH3; X2A′) collision complex. This insertion is followed by a hydrogen shift from germanium to carbon and unimolecular decomposition of the methylgermyl (GeH2CH3; X2A′) intermediate by atomic hydrogen elimination leading to singlet methylgermylene (HGeCH3; X1A′). Our investigation provides a glimpse at the largely unknown reaction dynamics and isomerization processes of the carbon‐germanium system, which are quite distinct from those of the isovalent carbon system thus providing insights into the intriguing chemical bonding of organo germanium species on the most fundamental, microscopic level.

“…The latter undergoes rapid intersystem crossing to the singlet manifold and singlet germylmethylene (HCGeH 3 ; X 1 A), which then isomerizes nearly instantaneously through a hydrogen shift to germylene (H 2 CGeH 2 ; X 1 A 1 ) followed by either decomposition via molecular hydrogen loss to afford 1-germavinylidene (H 2 CGe; X 1 A 1 ) or another hydrogen shift to afford methylgermylene (CH 3 GeH; X 1 A′) prior to unimolecular decomposition to 1-germavinylidene (H 2 CGe; X 1 A 1 ). The preparation of the unstable molecules with multiple bonds has been studied utilizing various methods, including laser flash photolysis, 35 matrix isolation, 32 electric discharge, 22 and vacuum gas−solid reactions. 36 However, directed gas-phase preparation of extremely unstable molecules and determination of the corresponding angular distribution and translational energy information without consecutive collisions and wall effects are still needed.…”

mentioning

confidence: 99%

“…This sequence of stability agrees well with previous calculations. 19,32 How can these products be formed? The calculations reveal that the reaction of ground state atomic carbon ( 3 P) with germane (X 1 A 1 ) is initiated on the triplet surface via barrierless insertion of carbon into one of the four germanium−hydrogen bonds forming triplet germylmethylene (HCGeH 3 ; a 3 A; 3 i1) residing 322 kJ mol −1 below the separated reactants.…”

mentioning

confidence: 99%

Gas-Phase Preparation of 1-Germavinylidene (H₂CGe; X¹A₁), the Isovalent Counterpart of Vinylidene (H₂CC; X¹A₁), via Non-adiabatic Dynamics through the Elementary Reaction of Ground State Atomic Carbon (C; ³P) with Germane (GeH₄; X¹A₁)

Sun

et al. 2023

J. Phys. Chem. Lett.

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1-Germavinylidene (H 2 CGe; X 1 A 1 ), the germanium analogue of vinylidene (H 2 CC; X 1 A 1 ), was prepared via a directed gas-phase synthesis through the bimolecular reaction of ground state atomic carbon (C; 3 P) with germane (GeH 4 ; X 1 A 1 ) under singlecollision 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 (H 2 GeCH 2 ), which predominantly decomposes via molecular hydrogen loss to 1-germavinylidene (H 2 CGe; X 1 A 1 ). 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 (H 2 CGe) 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.