- Heteroorganic betaines 3. * Reactions of betaines containing the +P-C-Si-S- fragment
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The [Ph3P+-CMe2-SiMe2-SEt]Br- salt was prepared by the reaction of betaine Ph3P+-CMe2SiMeR-S- (1a: R = Me) with EtBr. Acetylation of betaine 1a or Et3P+-CHMeSiMe2-S- (2a) afforded 2,2,6-trimethyl-1,3-dioxa-2-silacyclohex-5-ene-4-thione Me2SiOC(=S)CH=C(Me)O or the [Et3P+-CHMeSiMe2Cl]Cl- salt depending on the reagent ratio. The reactions of betaines 1a,b (1b: R = Ph) or 2 with compounds (R3Sn)2X (X = O or NMe) can be used for the generation of silanones [RMeSi=O] and silaneimines [RMeSi=NMe] in solutions. The reactivity of betaines Ph3P+-CHR1SiMeR2-S- (R1 = H or Me and R2 = Me or Ph) is determined by the equilibrium between the zwitterionic and ylide Ph3P=CR1SiMeR2SH tautomers that exist in solutions.
- Borisova,Zemlyanskii,Shestakova,Khrustalev,Ustynyuk,Chernyshev
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p. 933 - 941
(2007/10/03)
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- A new method for generating organosilanones
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A new method for the generation of organosilanones by the reaction of betains, R3P+-CR1R2-SiR3R4-S-, with (Et3Sn)2O was suggested. - Key words: organosilicon-phosphorus betaine; organosilan
- Zemlyansky, N. N.,Borisova, I. V.,Shestakova, A. K.,Ustynyuk, Yu. A.,Chernyshev, E. A.
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p. 2126 - 2127
(2007/10/02)
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- On the Problem of the Intermediate Formation of Silanone R2Si=O by Reactions of Silenes with Dinitrogen Oxide
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The silaethene Me2Si=C(SiMe3)2 (1a; unstable; from 1a * Ph2C=MSiMe3 = 4) forms with N2O an unstable cycloadduct, which decomposes under isomerization or cleavage.It was not possible to decide clearly, whether the last reaction, which leads to (Me3Si)2CN2 and polymers with (Me2SiO)n groups, proceeds with intermediate formation of silanone Me2Si=O or not (no trapping product with Et3SiH, but with Me3SiCl).The silanimines Me2Si=NSitBu3 (2a; unstable; from 2a * tBu3SiN3 = 7) and tBu2Si=NSitBu3 (2b; metastable) form with N2O unstable cycloadducts, which, under participation of the silanimines, react into products (10) being composed of a molecular silanone and a molecule silanimine.As has been shown by trapping experiments with Et3SiH, Me3SiCl, or Me3SiOMe, latter reaction involves unstable free silanones Me2Si=O (3a) or tBuSi=O (3b) as intermediates. 3b, generated in benzene from 2b/NO2 in the presence of equimolar amounts of tetrahydrofuran (THF), obviously forms an adduct 3b*THF, which is trapped by excess 2b.When 3b is produced in THF as solvent, the silanone starts THF polymerization, indicating a high Lewis acidity of silanones.
- Wiberg, Nils,Preiner, Gerhard,Schurz, Klaus
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p. 1407 - 1412
(2007/10/02)
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- Reaction of O(3P) with Hexamethyldisilane
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The title reaction has been investigated at room temperature in a discharge flow system and also by stationary Hg(3P1)-sensitized N2O photolysis experiments.By far the most important reaction is the insertion of O(3P) atoms into the Si-Si bond yielding a vibrationally excited hexamethyldisiloxane.The rate constant for this reaction has been measured to be (1.3 +/- 0.3) x 10-13 cm3 s-1.The vibrationally excited hexamethyldisiloxane could not be stabilized at pressures up to 1 bar, decomposing mainly by Si-C bond cleavage.A reaction mechanism is proposed to account for the observed products.
- Hoffmeyer, H.,Potzinger, P.,Reimann, B.
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p. 4829 - 4831
(2007/10/02)
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