129439-04-9Relevant articles and documents
Difluorocarbene insertion into Si-H bonds: the preparation and properties of difluoromethylsilanes
Buerger, H.,Eujen, R.,Moritz, P.
, p. 249 - 260 (2007/10/02)
Difluorocarbene, CF2, generated by thermal decomposition of CF3SiF3 at 100 deg C, has been found to insert into the Si-H bonds of halosilanes SiH3X (X = F, Cl, Br, I), methylhalosilanes CH3SiH2X (X = Br, Cl) and (CH3)2SiHCl, and disiloxane (SiH3)2O.Use of excess of the CF2-source CF3SiF3 and of pressure favour the formation of the di-insertion products (CHF2)2SiHX and (CHF2)2(CH3)SiX. (CHF2)3SiCl was identified among the products formed in the co-thermolysis of CF3SiF3 and (CHF2)SiH2Cl.In contrast, organosilanes RnSiH4-n (R = Me, Ph; n = 0-4), dihalosilanes SiH2X2 and RSiHX2, trihalosilanes HSiX3 and tetrahalosilanes SiX4 do not react with CF2 under these conditions.The reactivity and selectivity of difluorocarbene is discussed in terms of steric and electronic parameters.A kinetic deuterium effect, k(SiH)/k(SiD) 1.14, has been observed for the insertion into MeSiH2Cl.The mostly novel products were characterized by vibrational and multinuclear NMR spectroscopy.Difluoromethylsilane, (CHF2)SiH3, has been obtained from (CHF2)SiH2Cl and LiAlH4 in almost quantitative yield, and its vibrational spectrum has been recorded and interpreted with the assistance of a normal coordinate analysis.
Thermolysis of trifluoromethylsilanes. Novel fluoromethylsilanes by insertion of CF2 and CHF into Si-H bonds
Beckers, H.,Buerger, H.
, p. 207 - 219 (2007/10/02)
The thermal decomposition in the gas phase of CF3SiH3 and (CF3)2SiH2 begins at ca. 200 and ca. 100 deg C, respectively.It is catalyzed by KF, and involves as initial step a clean CF2 elimination with an α-fluorine shift.Reactive species such as HBr trap CF2 quantitatively (to give in this case CHF2Br), while addition to the less reactive cyclohexene (to give 7,7-difluorobicycloheptane) is accompanied by secondary reactions.These dominate in the absence of an efficient CF2 trapping agent, and spectroscopic product analyses reveal that they mainly arise from insertion of the carbenes CHnF(2-n) into Si-H bonds followed by CH(n+1)F(1-n) elimination (n = 0, 1).This sequence corresponds to H/F exchange at the Si atom.Insertion of CF2 (generated by thermolysis of CF3SiF3 below 100 deg C) into an Si-H bond of H3SiF to give CHF2SiH2F in good yield is the first example of such a reaction and demonstrates its usefulness for the selective synthesis of CHF2Si compounds.In addition, some dismutation of SiHnF(3-n) moieties accompanies the carbene elimination/insertion reactions and the resulting novel fluoromethylsilanes were characterized by 1H and 19F NMR and (in part) IR spectroscopy.The synthesis of (CF3)2SiHBr by cleavage of (CF3)2Si(H)N(i-Pr)2 with BBr3 and its conversion with LiAlH4 to (CF3)2SiH2 are reported.The mechanism of the CF2/SiH insertion reaction is discussed.
