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 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
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.
