V.F. Kalasinsky

The determination of the potential function governing the low frequency bending mode of disiloxane

The Raman spectra (10–3500 cm−1) of gaseous and solid disiloxane and disiloxane‐d6 have been recorded. The infrared spectra of the gas from 4000 to 30 cm−1 and of the solid from 4000 to 450 cm−1 have been investigated. An examination of the low frequency Raman spectrum of the gas under moderately high resolution conditions (1.0 cm−1) revealed a Q‐branch series for each molecule attributable to the double jumps of the anharmonic, low‐frequency skeletal bending mode. The observed Q‐branches were assigned with the help of a potential function of the form V (cm−1) =1.07±0.02 q4−21.9±0.3 q2 for the ’light’ compound and V (cm−1) =0.973±0.015 q2−19.2±0.4 q4 for the deuterated compound, where q is one of the reduced polar coordinates q and φ. These functions lead to barriers to linearity of 112±5 and 95±5 cm−1, with the ground state energy levels at 42.6 and 37.8 cm−1, respectively. Transformation of the potential functions to dimensioned form by using the reduced masses for the bending vibration gives an average...

Spectra and structure of small ring compounds: Part XXXV. Vibrational spectra and ring-puckering and torsional potential functions of cyclobutylamine

Abstract The IR spectra (50–4000 cm −1 ) of gaseous and solid cyclobutylamine and cyclobutylamine-N- d 2 and the Raman spectra (25–4000 cm −1 ) of gaseous, liquid and solid cyclobutylamine and cyclobutylamine-N- d 2 have been recorded. Depolarization values were measured for both the gaseous and liquid states. Most of the thirty-six fundamental vibrations have been assigned and support for more than one molecular configuration is presented. In the low frequency region for the “light” compound, a series of four Q -branches have been assigned to transitions between energy levels of the ring-puckering vibration for the equatorial isomer. The transitional frequencies were fitted to an asymmetric single-minimum potential function of the form: V(X) = 0.474 × 10 6 X 4 - 0.204 × 10 5 X 2 + 0.993 × 10 5 X 3 with a reduced mass of 160 amu. The following torsional potential constants were determined for the “light” molecule- V 1 = 77.8 ± 17.0 cm −1 , V 3 = 784.0 ± 3.3 cm −1 . The trans conformation was found to be more stable than the gauche form by approximately 58 cm −1 (0.17 kcal mol −1 ). The barriers to trans-gauche , gauche-trans , and gauche-gauche interconversion are 803, 745 and 803 cm −1 , respectively.

Raman spectra of gases: XIV. Hexachlorodisiloxane

Abstract The Raman spectra (50–1200 cm −1 ) of gaseous, liquid, and solid (Cl 3 Si) 2 O have been recorded. The infrared spectra of the gas and solid have been recorded from 55–2000 cm −1 . The spectra of the gas have been interpreted in detail on the basis of C 2v symmetry with the A 1 skeletal Si-O-Si bend assigned at 63 cm −1 . The spectra gave evidence that there are structural changes upon condensation of the gas and the Si-O-Si angle approaches linearity in the solid state. The opening of this angle is probably due to crystal packing factors.

Spectra and structure of phosphorus-boron compounds: VII. Vibrational analysis of solid phosphine-borane

Abstract The infrared (70–2700 cm − ) and Raman (25–2500 cm −1 ) spectra of H 3 PBH 3 , H 3 PBD 3 , D 3 PBH 3 and D 3 PBD 3 in the solid state at −196 °C have been recorded. The shift associated with the boron-10 and boron-11 isotopes was observed for the P-B stretching motion. A complete vibrational assignment is proposed and a normal coordinate calculation utilizing a valence force field model has been carried out. The force constant of 1.97 mdyn A −1 for the phosphorus-boron stretching mode is consistent with the relatively long phosphorus-boron bond; this constant is compared to the similar quantity for several other phosphorus-boron compounds. None of the E modes for the “free” molecule were found to be split. The number of observed lattice modes is not consistent with the crystal structure previously reported for this molecule. A possible explanation is discussed.

Spectra and structure of organophosphorus compounds: XIII. Microwave, raman and infrared spectra of CH3POF2

Abstract The microwave spectrum of methylphosphonic difluoride, CH3POF2 has been investigated in the region between 18.5 and 40.0 GHz. R-branch assignments have been made for the ground and two excited vibrational states for the a-type transitions. The rotational constants were found to be A = 4495.52 ± 0.04, B = 4271.84 ± 0.03 and C = 4125.93 ± 0.03 MHz The values of the dipole moment components were obtained from Stark splittings to be: ¦μa¦ = 3.4 ± 0.2; ¦μc¦ = 0.4 ± 0.5; and ¦μt¦ = 3.62 ± 0.2 D. The Raman spectra of CH3POF2 have been recorded in both the gas and solid phases and vibrational assignments are proposed for the fundamentals. The overtone and fundamental of the methyl torsion were observed in the Raman and IR spectra, respectively. The observed splitting from the microwave spectra of vibrationally excited states of the torsion led to the calculation of the barrier to internal rotation of 3.58 ± 0.04 kcal mol−1. This value is consistent with the torsional frequencies observed in the vibrational spectrum. This barrier value is compared to similar quantities in related molecules.

Vibrational spectra and molecular symmetry of tetrasilylhydrazine and tetrasilylhydrazine-d12

Abstract The Raman spectra of tetrasilylhydrazine and tetrasilylhydrazine- d 12 have been recorded for the gas, liquid and solid phases from 25 to 2500 cm −1 . The infrared spectra of N 2 (SiH 3 ) 4 and N 2 (SiD 3 ) 4 have been recorded for the gas and solid phases from 40 to 2500 cm −1 . The vibrational data have been interpreted on the basis of a twisted ( D 2d ) molecular configuration for both the fluid and solid states.

Spectra and structure of phosphorus-boron compounds, XII1 Vibrational spectra and molecular symmetry of tetramethylbiphosphine-bisborane

The infrared (200–3500 cm−1) and Raman (50–3500 cm−1) spectra of two isotopic species of tetramethylbiphosphine-bisborane, (CH3)4P2·2BH3 and (CH3)4P2·2BD3, in the solid state at low temperatures have been recorded. The spectra have been interpreted in detail on the basis ofC2h molecular symmetry. The P-B stretching modes were assigned to bands at 599 and 567 cm−1 in the Raman and infrared spectra of the “light” compound, respectively. Only one P-P stretching mode was observed in the Raman spectra. The vibrational data appear to be consistent with the presence of only one conformer in the solid state, which is at variance with the conclusions from an X-ray study. Considerable splitting of the low-frequency bending modes was observed for both compounds; this splitting has been attributed to the factor group.

Spectra and structure of phosphorus-boron compounds—XIV. Vibrational study of P-hexamethylcyclotriborophosphane, [(CH3)2PBH2]3.

Abstract The i.r. spectra of solid (3500-30 cm −1 ) and gaseous (3500-200 cm −1 ) P -hexamethylcyclotriborophosphane have been recorded along with the Raman spectra (3500-10 cm −1 ) of the solid, liquid, and gas. The vibrational data have been interpreted in detail on the basis of C 3υ molecular symmetry. The observed intermolecular vibrations in the solid state indicate only slight factor group effects. The molecular structure of P -hexamethylcyclotriborophosphane is discussed in relation to X-ray diffraction and recent NMR data.

Spectra and structure of phosphorus-boron compounds—XVI. Vibrational studies of P-octamethylcyclotetraboraphosphane

Abstract The i.r. spectra of P-octamethylcyclotetraboraphosphane was examined in the solid phase (3500-30 cm −1 ) and in the gaseous phase (3500-200 cm −1 ). The Raman spectra of this compound (3500-10cm −1 ) were recorded in the solid and liquid phases. The vibrational spectra are consistent with D 2d symmetry in all phases. There appears to be minimal factor group effects in the solid phase. The results are discussed in relation to recent NMR work and vibrational work with the closely related six-membered boron phosphorus rings.