E. C. Curtis

Vibrational spectra of the pseudotrigonal bipyramidal tetrafluorides SF4 and CIF4

Abstract The Raman spectra of gaseous, liquid and solid SF 4 have been re-examined. Polarization measurements allow the unambiguous identification of the A 1 modes. The i.r. spectrum of SF 4 isolated in N 2 matrix has been recorded and 32 S 34 S isotopic shifts have been measured for several fundamentals. The matrix isolation study indicates that the 353 cm −1 absorption consists of two fundamentals, thus providing the hitherto missing ninth fundamental of SF 4 . Complete assignments are given for SF 4 and are supported by force field and mean amplitudes of vibration computations. The results from the vibrational analysis support an intramolecular Berry-type exchange mechanism for SF 4 . Raman polarization data have also been obtained for CIF 4 + SbF 6 − in HF solution and revised assignments and force field values are given for CIF 4 + .

The CF3O− anion: Vibrational spectrum of an unusual CF3 compound

Abstract The i.r. and Raman spectra of solid CsOCF 3 and the Raman spectra of liquid and gaseous NF 3 O have been recorded. The vibrational spectrum of CF 3 O − closely resembles that of isoelectronic NF 3 O. For CF 3 O − , six fundamentals were observed and assigned consistent with a pseudo-tetrahedral structure of symmetry C 3 v . It is shown that the unusual bonding in NF 3 O is not unique but also occurs in CF 3 O − . In both isoelectronic X F 3 O species, the X O bond possesses almost double bond character whereas the three X F bonds are highly polar implying very strong contributions from resonance structures such as The occurrence of this type of bonding can be rationalized by the high electronegativity of fluorine and by the importance of the octet rule for first row elements limiting the sum of the bond orders to a maximum of four.

Vibrational spectrum and normal coordinate analysis of SF5Br

Abstract The i.r. spectrum of gaseous and the Raman spectrum of liquid SF5Br are reported. Ten out of 11 fundamentals expected for symmetry C4υ were observed and assigned. A normal coordinate analysis was carried out and thermodynamic properties in the range 0–2000 K were computed.

The vibrational spectra of dimethyl sulfates

Abstract Infrared and Raman spectra were recorded for liquid CH3OSO2OCH3 and CD3OSO2OCD3. With the exception of one torsional mode, all fundamental vibrations expected for the COSO2OC skeleton were observed and assigned on the basis of symmetry C2v.

Reparameterized vibrational force constants—I: Method and application to four square-pyramidal molecules

Abstract Vibrational force constants of polyatomic molecules can be more conveniently calculated by least squares when the adjustments are computed for orthogonal linear combinations of the force constants. Beparameterizing the force constants to an orthogonal space is discussed and a method of error analyses described. It is argued that in addition to speeding calculation, this is a statistically sound method of treating underdetermined systems. As an example, force constants with error analyses are reported for XeOF 4 , IF 5 , BrF 5 , and ClF 5 .

Vibrational spectra of thionyl tetrafluoride, SF4O

Abstract The i.r. spectra of gaseous, solid, and matrix-isolated SF 4 O and the Raman spectra of gaseous, liquid and solid SF 4 O are reported. It is shown that several bands previously attributed to SF 4 O belong to impurities, and 8 of the 12 fundamentals of SF 4 O were reassigned. A normal coordinate analysis was carried out and indicates for SF 4 O a structural model with significantly longer axial than equatorial SF bonds, in disagreement with Gundersen and Hedbergs favored Model A . Thermodynamic properties are also reported for SF 4 O.

Vibrational spectrum of bromine trifluoride

Abstract The infrared spectrum of matrix isolated BrF 3 has been recorded. All six fundamental vibrations expected for a T -shaped molecule of symmetry C 2 v were observed. A modified valence force field and some thermodynamic properties have been computed for BrF 3 .

Infrared spectrum of ClOSO2F

Abstract The infrared spectra of gaseous and solid ClOSO 2 F have been measured. Ten of the 12 fundamentals were observed and a vibrational assignment for symmetry C 3 is suggested. Some thermodynamic properties and principal force constants have been computed.

Vibrational spectrum and force constants of the XeF5+ cation

Abstract The i.r. and Raman spectra of solid XeF5+BF4− and XeF5+AsF6− and their Raman and 19F NMR spectra in HF solution were recorded. The observed spectra are consistent with a square-pyramidal XeF5+ cation of symmetry C4v. All nine fundamentals were assigned for XeF5+ and force constants were computed for the isoelectronic series XeF5+, IF5, TeF5− and SbF52−.