The molecular structure of bis(pentafluorosulfur)methane (SF 5) 2CH 2 and perfluorovinylsulfur pentafluoride SF 5CFCF 2

Abstract

The geometric structures of bis(pentafluorosulfur)methane and perfluorovinylsulfur pentafluoride were determined by gas-phase electron diffraction. The following skeletal geometric parameters ( r a distances and ∠ α angles with 3σ estimated uncertainties) were derived for (SF 5) 2CH 2:SF e = 1.570(4) Å, SF a = 1.578(13) Å, SC = 1.832(6) Å, ∠SCS = 126.1(8)° and ∠F aSF e = 88.2(2)° (F e and F a are equatorial and axial fluorine atoms, respectively). The molecule possesses C 2 symmetry and the SF 5 groups are twisted by 9.6(16)° from the staggered positions with C 2v overall symmetry. The experimental electron diffraction intensities of SF 5CFCF 2 are consistent with C s symmetry and the vinyl group staggered with respect to the equatorial SF bonds. The relevant geometric parameters are: SF e = 1.571(3) Å, SF a = 1.537(11) Å, SC = 1.784(8) Å CC = 1.310 Å (assumed), (CF) mean = 1.311(3), Å ∠SCC = 126.5(8)° and ∠F aSF e = 88.9(3)°. The SC bond lengths in these two compounds are discussed in comparison with bonds in other SF 5 derivatives which contain sp 3, sp 2 or sp hybridized carbon atoms.