An extended simultaneous kinetics and ringdown model: Determination of the rate constant for the reaction SiH₂ + O₂

What have we learnt about heavy carbenes through laser flash photolysis studies?

“…The reaction of SiH 2 with O 2 is one with very little if any pressure dependence. Our data 46 suggests a slight lowering of the rate constant at 1 Torr (SF 6 ) at each of five temperatures in the range 297-600 K while that of Guo et al 73 records no dependence between 1.9 and 260 Torr (Ar) at 298 K. If there is any pressure dependence, it is probably connected with collisionally induced intersystem crossing in the H 2 SiOO adduct (the silicon analogue of the Criegee intermediate), because ab initio studies 46,73 show that energy release is so great that any singlet state intermediates will almost certainly fragment to product pairs, e.g. H 2 O + SiQO.…”

Molecular Main Group Metal Hydrides

“…We would like to draw specific attention to the review by Hadlington, Driess, and Jones who document the use of modern molecular design principles and synthetic methods to access low-coordinate Group 14 hydride complexes, while discussing important pioneering work relating to the use of such species in catalysis . The parent inorganic silylene SiH 2 is often touted as a key intermediate formed during the decomposition of SiH 4 into thin films of Si. , As shown in Scheme , SiH 2 can be generated as a transient species by the flash photolysis of PhSiH 3 , while photolysis of Me 2 SiH 2 and 1-chloro-1-silacyclopent-3-ene ( 738 ) yield MeSiH and ClSiH, respectively. , The reactivity of SiH 2 with small molecules, such as O 2 , H 2 O, HCl, CO 2 , MeC­(O)­H, Me 2 O, alkenes, , alkynes, N 2 (the H 2 Si·N 2 adduct is stable at 10 K), NO, or silanes (e.g., MeSiH 3 ), can lead to E–H bond insertion, oxidative addition, hydride migration, or Lewis acid–base adduct formation, depending on the nature of the substrate (Scheme ). Furthermore, SiH 2 also has been the subject of numerous computational investigations. − Laser flash photolysis of germacyclopentenes at 193 nm (Scheme ) yields GeH 2 , either in the gas phase or solution, , and reactivity paths that mirror those exhibited by SiH 2 with small molecules have been observed. − In related work, gas phase laser flash photolysis of 1,3,4-trimethyl­germacyclopent-3-ene ( 739 ) yields transient MeGeH (Scheme ), while passage of an electric discharge through H 3 GeCl vapor affords the reactive halogermylene HGeCl .…”

Time-resolved gas-phase kinetic and quantum chemical studies of the reaction of silylene with oxygen

“…Comparison with previous studies at room temperature shows good consistency. CBEJ 13 obtained values for the rate constant of (7.5 AE 0.8) Â 10 À12 cm 3 molecule À1 s À1 at 1 Torr and (1.4 AE 0.2) Â 10 À11 cm 3 molecule À1 s À1 at 9.5 Torr in He buffer gas (and an intermediate value at 5 Torr He), while GFFT 14 obtained an average value of (1.64 AE 0.32) Â 10 À11 cm 3 molecule À1 s À1 independent of pressure (Ar buffer gas) between 1.9 and 260 Torr. Allowing for systematic error, our value of (1.64 AE 0.16) Â 10 À11 cm 3 molecule À1 s À1 at 10 Torr (SF 6 buffer gas) is in excellent agreement with both studies.…”