287-29-6Relevant academic research and scientific papers
Conformational Equilibrium in 1-Fluoro-1-silacyclobutane as Studied by Microwave Spectroscopy and ab Initio Calculations
Melandri, Sonia,Favero, Laura B.,Caminati, Walther,Grosser, M.,Dakkouri, Marwan
, p. 223 - 236 (1995)
The microwave spectrum of 1-fluoro-1-silacyclobutane has been investigated in the frequency range 26-40 GHz.The spectra of the equatorial and axial conformers and of several vibrational satellites, mainly belonging to the ring-puckering progression, have been assigned.The shifts of the rotational constants with respect to the ground state, together with the relative intensities and the dipole moments, have been used to obtain the shape of the potential energy function hindering the ring-puckering.The experimental results agree well with 6.31G* calculations.
Method of preparing silacycloalkanes
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, (2008/06/13)
According to the present invention, a method of preparing a silacycloalkane, comprising the steps of (A) adding a substituted silacycloalkane having the formula: wherein X1is —F, —Cl, —Br, or —OR1and X2is X1or H, wherein R1is C1-C8hydrocarbyl, and n is 1, 2, or 3, to a suspension of lithium aluminum hydride in a glycol diether at a temperature not greater than 50° C. to form a mixture, wherein the glycol diether consists essentially of a linear arrangement of oxyalkylene units having formulae independently selected from —OCH2CH2—, —OCH2CH(CH3)—, and —OCH2CH(CH2CH3)—, and end-groups having the formulae —R2and —OR2, wherein each R2is independently selected from C1-C8alkyl, phenyl, and C1-C8alkyl-substituted phenyl, provided the glycol diether has a normal boiling point of at least 85° C. and a viscosity not greater than 3000 mm2/s at 25° C.; and (B) distilling the mixture under reduced pressure at a temperature not greater than 50° C. to remove the silacycloalkane.
Structural and conformational analysis of 1-monofluorosilacyclobutane and 1-monochlorosilacyclobutane. A gas-phase electron diffraction and ab initio investigation
Dakkouri,Grosser
, p. 7 - 24 (2007/10/03)
The structures of numerous 1,1-disubstituted silacyclobutanes have been investigated thoroughly, but none of the monosubstituted representatives have been studied as yet. In the present work the geometric structures and conformational equilibria of 1-monofluorosilacyclobutane (MFSCB) and 1-monochlorosilacyclobutane (MCSCB) have been investigated by means of gas-phase electron diffraction and ab initio calculations. The conformational analysis reveals that both molecules are present with both equatorial and axial conformations. Consistent with one another, the electron diffraction data and the ab initio results show that the equatorial conformers of MFSCB and MCSCB are more stable than the higher energy axial forms. The experiments demonstrate that the equatorial conformers of MFSCB and MCSCB are lower in energy than the axial conformers by 4.30 (0.21) kJ/mol (corresponding to eq: ax = 85: 15 (5)) and 3.92 (0.23) kJ/mol, (eq: ax = 83: 17 (6)), respectively. For comparison, ab initio calculations at the MP/6-31G(d,p) level predict energy differences of 6.04 and 3.43 kJ/mol, respectively, in favor of the equatorial forms of MFSCB and MCSCB. During the structural refinement it was assumed that all of the structural parameters except the puckering angle Θ for both the equatorial and axial conformers are equal. This assumption was supported by the ab initio calculations. The major (ra) bond distances and bond angles which were obtained from the final refinement of the experimental data are (with uncertainties of 3σ) for MFSC: r(Si-C) = 1.855(1) A?, r(Si-F) = 1.592(2) A?, r(C-H) = 1.089(3) A?, ∠(H-Si-F) = 106.8(6)°, ∠(C-Si-C) = 80.8(6)°, ∠(C-C-C) = 98.6(19)° and the puckering angles Θeq = 37.4(20)° and Θax = 23.5(70)°. For MCSCB the following structural parameters were obtained: r(Si-C) = 1.864(2) A?, r(Si-Cl) = 2.059(3) A?, r(Si-H) = 1.470(12) A?, r(C-C) = 1.591(5) A?, r(C-H) = 1.112(4) A?, ∠(H-Si-Cl = 106.0(6)°, ∠(C-Si-C) = 80.7(14)°, ∠(C-C-C) = 98.7(22)°. The puckering angles were found to be Θeq = 34.2(25)° and Θax = 21.5(50)°. The observed simultaneous reduction of the Si-C and the Si-F(Cl) bonds can be examined by electrostatic arguments and other concepts such as bond polarity, negative hyperconjugation and carbon(2pπ)-silicon(3pπ) orbital overlap. By applying various ab initio methods such as HF/6-31G(d,p), MP2/6-31G(d,p) and DFT/b3pw91/6-31G(p) the structures and conformations of mono- and dihalogenated silacyclobutanes of the type (CH2)3SiY (Y = HF, HCl, HBr, HI, H2, F2, Cl2, Br2 and I2) have been investigated. Our results show that there is a regular increase of the preferability of the equatorial conformer with the increase of the electronegativity of the halogen atom. This finding is consistent with the correlation which was postulated earlier by Jonvik and Boggs [4-7] for monosubstituted cyclobutanes. In order to gain more insight regarding the influence of the electronegativity of the substituent on the degree of strain in silacyclobutanes and for the purpose of comparison of the structures of different mono- and dihalogenated acyclic silanes and silacyclic compounds of larger size, as silacyclopentane and silacyclohexane have been also computed.
SILAETHENE I. DARSTELLUNG UND CHARAKTERISIERUNG VON MONOSILACYCLOBUTANEN
Auner, N.,Grobe, J.
, p. 25 - 52 (2007/10/02)
Monosilacyclobutanes of the type RR' are prepared by ring closure reactions of 3-halopropylhalosilanes and by substitution of SiCl containing silacyclobutane rings with organometallic reagents (RMgX, LiR, NaCp).Under optimal experimental conditions yields between 50 and 95percent can be obtained by both procedures.Characterization of the compounds is accomplished by analytical (C, H, N) and NMR, IR and mass spectroscopic investigations.
