373-74-0Relevant articles and documents
(p-d) ? Bonding in Fluorosilanes? Gas-Phase Structures of (CH3)4-nSiFn with n = 1-3 and of t-Bu2SiF2
Rempfer, Beate,Oberhammer, Heinz,Auner, Norbert
, p. 3893 - 3897 (1986)
The gas-phase structures (rg values) of the methylfluorosilanes (CH3)4-nSiFn with n = 1-3 and of di-tert-butyl-difluorosilane, t-Bu2SiF2, have been determined by electron diffraction.In the case of CH3SiF3 the microwave rotational constant was included in the structure analysis.In the methylfluorosilane series a steady decrease of Si-F and Si-C bond lengths is observed with increasing fluorination: Si-F = 1.600(2), 1.586(2), and 1.570(2) Angstroem and Si-C = 1.848(2), 1.836(2), and 1.828(4) Angstroem for (CH3)3SiF, (CH3)2SiF2, and CH3SiF3, respectively.These trends are rationalized by increasing polar contributions and contraction of the silicon valence shell.Ab initio calculations for SiF4 indicate that (p-d) ? bonding is negligible.Substitution of the methyl groups in (CH3)2SiF2 by tert-butyl groups leads to lengthening of Si-F and Si-C bonds and strong variations in the silicon bond angles: Si-F = 1.586(2), 1.606(4) Angstroem; Si-C = 1.836(2), 1.869(3) Angstroem; CSiC = 116.7(6) deg, 125.5(11) deg; and FSiF = 104.6(4) deg, 97.7(8) deg in (CH3)2SiF2 and t-Bu2SiF2, respectively.
The vibrational spectra of germane and silane derivatives-X. Trifluoro(methyl)-silane and germane revised
Clark, Allan J. F.,Drake, John E.
, p. 391 - 398 (1981)
A reinvestigation of the vibrational spectra of CH3SiF3 has lead to a more complete assignment than is currently available.An extension of the methods used has promoted a reassignment of the skeletal modes of CH3GeF3 and is believed to have lead to a settling of the assignment of CH3GeCl3, for which several version exist.
Conversion of Poly(methylhydrosiloxane) Waste to Useful Commodities
D?hlert, Peter,Enthaler, Stephan
, p. 345 - 352 (2016/02/23)
Poly(methylhydrosiloxane) [PMHS, R(OSiMeH)nOR] is applied in chemistry as cheap, low-toxic, air and moisture stable reducing reagent. However, along with the desired products significant amounts of silicone waste is produced, since only ~1.7 % of the PMHS is employed for the reduction process. The formation of PMHS-waste reduces the sustainability of such reduction protocols. For instance PMHS can be applied as reagent (a) in the methanolysis to produce molecular hydrogen; (b) in the reduction of sulfoxides to form the corresponding sulfides; (c) in the hydrodeoxygenation of fatty esters to produce hydrocarbons. An option for the treatment of the PMHS-waste can be the application of depolymerization methods to convert it to useful commodities. In more detail, the silicone waste is reacted in a depolymerization reaction with boron trifluoride diethyl etherate (BF3OEt2) to produce methyltrifluorosilane (MeSiF3) and difluoromethylsilane (MeSiF2H), which can be interesting building blocks for the silicone industry, overall demonstrating a resource conserving process.
The synthesis and properties of (CH2F)SiH3 and related monofluoromethylsilanes
Buerger, H.,Moritz, P.
, p. 293 - 308 (2007/10/02)
The reduction of (CFCl2)SiCl3 by LiAlH4, Me3SnH, and (nBu)3SnH has been studied.The compound (CH2F)SiH3 (I) and all the compounds of the series (CFCl2-mHm)SiCl3-nHn, m = 0, 1 and n = 0-3 were detected and characterized by NMR spectroscopy.Conditions for the synthesis of I, (CHFCl)SiH3 (IX) and (CFCl2)SiH3 (V) with acceptable yields have been optimized.These novel compounds were studied by 1H, 19F, 13C and 29Si NMR spectroscopy; their infrared and Raman spectra were recorded and assigned with the assistance of a normal coordinate analysis of 1 and its isotopomer (CD2F)SiD3.The thermolyses of I, IX and (CHF2)SiH3 (X) which start at about 120, 200 and 180 deg C, respectively, have been studied.Whereas I decomposes by a migration of F from C to Si, compound X undergoes elimination of the carbene CHF, insertion of which into SiH bonds ultimately gives CH3Si derivatives.
Synthesis of alkyl fluorosilanes by the reaction of alkyl chlorosilanes with pyridinium poly(hydrogen fluoride) at room temperature
Muddukrishna, K. R.,Padma, D. K.
, p. 51 - 54 (2007/10/02)
Dimethyl difluorosilane (DFS) has been prepared in high yield (80-90percent) by the reaction of dimethyl dichloro-silane with pyridinium poly(hydrogen fluoride) at room temperature (25-35 deg C).The gas has been characterised by IR and 19F NMR spectroscopy, molecular weight measurements and elemental analysis.The method has been extended to the preparation in high yields of monomethyl and trimethyl fluorosilanes.
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.
Synthesis and Properties of Trimethyl(trifluorosilyl)stannane
D'Errico, John,Sharp, Kenneth G.
, p. 1879 - 1882 (2007/10/02)
Trimethyltin hydride reacts with SiF3SiF3 or SiF3SiF2H to give the new compound SnMe3(SiF3) in 75-80 percent yield.No reaction was observed between SnMe3H and SiF3SiH3.Hydrogen-deuterium exchange was observed between tin and silicon during the course of deuterium-labelling experiments.Dimethylstannylene (SnMe2) was implicated as an intermediate by trapping experiments in the thermolysis of SnMe3(SiF3).
Gas-Phase Lewis Acid-Base Interactions. An Experimental Determination of Cyanide Binding Energies from Ion Cyclotron Resonance and High-Pressure Mass Spectrometric Equilibrium Measurements
Larson, J. W.,Szulejko, J. E.,McMahon, T. B.
, p. 7604 - 7609 (2007/10/02)
Both ion cyclotron resonance and high-pressure mass spectrometric equilibrium techniques have been used to investigate the binding energies of anions to a variety of Lewis acids.From an analysis of the enthalpy changes associated with CN- binding it is evident that in cases of relatively weak binding considerable freedom of rotational motion of CN- in the complex may be retained.Ab initio calculations and experiment suggest that binding through both the N and C sites of CN- is nearly equally favorable in some cases.In contrast to results previously obtained for Bronsted acids which showed that CN- and Cl- bind nearly identically, the present data for Lewis acids show many cases where cyanide is much more favorably bound than chloride, a consequence of enhanced covalent binding of the CN- complexes.New Kroeger Drago parameters derived for CN- support the importance of covalent binding in cyanide adducts.Correlations of binding energy of anions to Lewis acids with the anion proton affinity show excellent linear relationships which may be used to predict binding energetics for new anions.
CHLOR-FLUOR -AUSTAUSCHREAKTIONEN MIT TRIALKYLFLUOR-PHOSPHORANEN
Bartsch, R.,Schmutzler, R.,Spiegel, G. U.,Stelzer, O.
, p. 107 - 118 (2007/10/02)
Trialkyldifluorophosphoranes R3PF2 (R = iPr, nBu) were found to react with chlorides or organoelement chlorides, EClm or ERm-zClz (EIV, m = 4, z = 1,2; EV, m = 3, z = 1,2) of elements belonging to main groups IV and V with chlorine/fluorine exchange to form the halophosphonium salts +Cl- (X = F, Cl) and the fluoro derivatives, EFm or ERm-zFz.With AlCl3 ionic products of composition are obtained.The transition metal chlorides, NiCl2, PdCl2 NiCl2(PMe3)2, and CoCl2 were found to be less reactive.Chlorine/fluorine exchange has been observed only the case of CoCl2.
