16571-41-8Relevant articles and documents
Reaction Of Hydrogen Atoms with Hexamethyldisilane
Ellul, R.,Potzinger, P.,Reimann, B.
, p. 2793 - 2796 (1984)
The reaction of hydrogen atoms with hexamethyldisilane has been studied by pulsed, mercury-sensitized photolysis experiments using Lyman α resonance absorption and resonance fluorescence detection of H atoms.At room temperature it proceeds exclusively according to H + (CH3)3SiSi(CH3)3 -> (CH3)3SiH (1) with a rate constant k(1) = (3.55 +/- 0.25)E-14 cm3 molecule-1 s-1 (T = 295 K).The temperature dependence of the rate constant in molecular units can be expressed by log k(1) = (-10.9 +/- 0.1) - The pseudo-first-order rate constant for H atom disappearance, K1, shows a dependence on the initial hydrogen atom to substrate concentration ratio.This is explained by two competing reaction channels for the disappearance of the trimethylsilyl radical: bimolecular combination (k(2)) and combination of hydrogen atoms with trimethylsilyl radicals yielding trimethylsilane (k(3)).From the intensity dependence of k1 and under the assumption that only reactions 1, 2, and 3 are operative, model calculations yield k(3) = (2 +/- 1)E-10 cm3 molecule-1 s-1, while for k(2) only an upper limit of 3 molecule-1 s-1 can be given.Thermochemical calculations suggest that the true value for k(2) is lower, probably close to the liquid phase values.
Photolysis of Hexamethyldisilane at 147 nm
Tokach, S. K.,Koob, R. D.
, p. 1 - 5 (1980)
Hexamethyldisilane vapor was photolyzed at 147 nm and various additives were used to intercept suspected reactive intermediates.The following primary products (quantum yields) were deduced from the product distribution of the collected experiments: (CH3)3Si (0.99), CH3 (0.51), (CH3)2SiCH2 (0.41), (CH3)3SiH (0.26), H (0.20), CH4 (0.08), and H2 (0.06).The cross disproportionation to combination ratio of CH3 and (CH3)3Si is determined to be 0.22 +/- 0.06 with no observable dependence on pressure or diluent (N2) concentration. (CH3)3Si abstraction of hydrogen competitive with radical recombination rates is also consistent with the results.The rate of reaction of (CH3)SiCH2 with methanol is found to be similar to that of (CH3)SiCH2 produced by photolyzing (CH3)4Si and 1,1-dimethyl-1-silacyclobutane; however, the pressure dependence found for this reaction in the last two systems is absent for (CH3)2SiCH2 produced in the photolysis of hexamethyldisilane.
Photolysis of some organosilylene precursors in a molecular beam
Huang, Yuhui,Sulkes, Mark,Fink, Mark J.
, p. 1 - 6 (1995)
The condensed-phase organosilylene precursors PhMeSi(SiMe3)2 (1), PhSi(SiMe3)3 (2), and (Me2Si)6 (3) were photolyzed in a molecular beam using a pulsed supersonic jet and mass spectrometric detection.Under ca. 10 ns pulsed UV illumination, we have found for the gas-phase trisilane precursors 1 and 2 that one photon results in removal of only one -SiMe3 group.Even at the highest laser power densities used, there is no evidence of removal of a second -SiMe3 to form a silylene.On the other hand, a single photolysis photon was capable of producing the silylene for the cyclohexasilane ring precursor, 3.Keywords: Silicon; Mass spectrometry; Molecular beams; Photochemistry
Homolytic cleavage of C-Si bond of p-trimethylsilylmethylacetophenone upon stepwise two-photon excitation using two-color two-laser flash photolysis
Cai, Xichen,Sakamoto, Masanori,Hara, Michihiro,Inomata, Susumu,Yamaji, Minoru,Tojo, Sachiko,Kawai, Kiyohiko,Endo, Masayuki,Fujitsuka, Mamoru,Majima, Tetsuro
, p. 402 - 406 (2007/10/03)
C-Si bond cleavage of p-trimethylsilylmethylacetophenone(1) occurred in a higher triplet excited state (Tn), giving mainly p-acetylbenzyl radical with the transient absorption in the region of 295-360 nm, with a quantum yield of 0.046 ± 0.008 using the two-color two-laser photolysis techniques. In contrast, the C-Si bond cleavage of p- trimethylsilylmethylbenzophenone(2) was absent in the Tn state whose energy is larger than the C-Si bond cleavage energy. The results can explain existence of a bond cleavage crossing between potential surfaces of the T n state and a dissociative state of the C-Si bond for 1, but not for 2.
Mechanism of the photodissociation of 4-diphenyl(trimethylsilyl)methyl- N,N-dimethylaniline
Tasis, Dimitrios A.,Siskos, Michael G.,Zarkadis, Antonios K.,Steenken, Steen,Pistolis, Georgios
, p. 4274 - 4280 (2007/10/03)
On irradiation in hexane (248- and 308-nm laser light) 4- diphenyl(trimethylsilyl)methyl-N,N- dimethylaniline, 2, undergoes photodissociation of the C-Si bond giving 4-N,N-dimethylaminotriphenylmethyl radical, 3(·) (λ(max) at 343 and 403 nm), in very high quantum yield (Φ = 0.92). The intervention of the triplet state of 2 (λ(max) at 515 nm) is clearly demonstrated through quenching experiments with 2,3-dimethylbuta-1,3- diene, styrene, and methyl methacrylate using nanosecond laser flash photolysis (LFP). The formation of 3(·) is further demonstrated using EPR spectroscopy. The detection of the S1 state of 2 was achieved using 266-nm picosecond LFP, and its lifetime was found to be 1400 ps, in agreement with the fluorescence lifetime (τ(f) = 1500 ps, Φ(f)= 0.085). The S1 state is converted almost exclusively to the T1 state (Φ(T) = 0.92). In polar solvents such as MeCN, 2 undergoes (1) photoionization to its radical cation 2(·)+, and (2) photodissociation of the C-Si bond, giving radical 3(·) as before in hexane. The formation of 2(·)+ occurs through a two-photon process. Radical cation 2(·)+ does not fragment further, as would be expected, to 3(·) via a nucleophile(MeCN)-assisted C-Si bond cleavage but regenerates the parent compound 2. Obviously, the bulkiness of the triphenylmethyl group prevents interaction of 2(·)+ with the solvent (MeCN) and transfer to it of the electrofugal group Me3Si+. The above results of the laser flash photolysis are supported by pulse radiolysis, fluorescence measurements, and product analysis.
