Henry Selig

Raman Spectra of MoF6, TcF6, ReF6, UF6, SF6, SeF6, and TeF6 in the Vapor State

Raman spectra of MoF6, TcF6, ReF6, UF6, SF6, SeF6, and TeF6 have been observed for the gaseous state using laser excitation. Some assignments of fundamental frequencies have had to be revised from previously accepted values. The overtone 2ν6 was observed for all these gaseous hexafluorides and several other overtones were observed for some of the molecules. Considerable broadening of the eg and f2g fundamentals was observed for TcF6 and for ReF6. This broadening is attributed to dynamic Jahn–Teller coupling. The best currently available measured values of fundamental frequencies for all 15 hexafluoride molecules of known Oh symmetry are tabulated.

Vibrational Spectra of IOF5, OsOF5, and ReOF5

Raman spectra of IOF5, OsOF5, and ReOF5, and the infrared spectra of OsOF5 and ReOF5 are presented, all for the gaseous state. Complete assignments of fundamental frequencies are made, and these confirm the expected C4ν symmetry. Fundamental frequencies in cm−1 in the order, 4a1, 2b1, b2, and 4e, are: for IOF5, 927.0, 680.4, 640.2, 362.9, 647, 307, ∼  330, 710.3, 372.2, 343, and 204.8; for OsOF5, 962.6, 716.4, 644, 280.5, 644, 210, 332, 700.6, 263, 367, and 164; and for ReOF5, 989.8, 738.6, 643, 309, 652, 234, 334, 713.0, 260, 365, and 125 cm−1.

Infrared Spectra of VOF3 and POF3

The infrared spectrum of VOF3 has been studied and interpreted in terms of a C3v molecular symmetry. All six fundamentals have been observed: the a1 frequencies are 1057.8, 721.5, and 257.8 cm−1 and the e frequencies are 806, 308, and 204.3 cm−1. The infrared spectrum of POF3 has also been studied and the lowest e fundamental, earlier observed in the Raman spectrum, has been confirmed.

The vapour-pressures and other properties of ReF6 and ReF7☆

Vapour-pressures of ReF6 and ReF7 have been measured. The vapour-pressures are represented by the following equations: ReF6: solid I (−10·47− − 3·45°C) log10p = −2303·6T − 0·8327 log10T + 12·70721; solid II (−3·45°–18·5°C) log10p = −1765·4T − 0·1790 log10 T + 9·12298; liquid (18·5°–48·06°C) log10p = −1956·7T − 3·599 log10 T + 18·20814. ReF7: solid (−14·47°–48·3°C) log10p = −2205·8T − 1·4703 log10 T + 13·04321; liquid (48·3–74·61°C) log10p = −244·28T + 9·90825 log10 T − 21·58352. Values for the heats of vaporization and heats of transition are given. ReF6 undergoes a solid-solid transition at −3·45°C and melts at 18·5°C. ReF7 melts at 48·3°C. Some chemical properties of these compounds are described.

Vibrational Spectra of IF7 and ReF7

Raman spectra of IF7 and ReF7 have been observed for the first time in the vapor state. Infrared spectra of the vapors have also been re‐examined. Earlier difficulties regarding possible coincidences in the IF7 spectra have been removed. The data suggest that both molecules belong to symmetry group D5h, although there are some significant as yet unexplained differences between them.

REACTIONS OF TECHNETIUM HEXAFLUORIDE WITH NITRIC OXIDE, NITROSYL FLUORIDE, AND NITRYL FLUORIDE.

Abstract Reactions of technetium hexafluoride with nitric oxide, nitrosyl fluoride and nitryl fluoride gave the compounds NOTcF6, (NO)2TcF8 and NO2TcF7. Magnetic properties and i.r. spectra of these compounds were studied and compared with some analogous complexes of the hexafluorides of tungsten, rhenium and osmium. Attempts to prepare NOTcF7 were unsuccessful.

Infrared and Raman Spectra of ClF3 and BrF3

The infrared and Raman spectra of the interhalogens ClF3 and BrF3 have been studied in the vapor phase. Frequencies for the six fundamental vibrations of each molecule have been assigned based on C2ν symmetry. For ClF3 the frequencies are 752.1, 529.3, and 328 (a1), 702 and 442 (b1), and 328 (b2) cm−1. For BrF3 they are 675, 552, and 242 (a1), 612 and 350 (b1), and 242 (b2) cm−1.

Raman Spectra of AsF5 and VF5 and Force Constants for PF5, AsF5, and VF5

Raman spectra are presented for AsF5 and VF5 in which all allowed fundamentals and several overtones are observed. Force constants and normal modes of PF5, AsF5, and VF5 are discussed in terms of the orbital‐valency–force‐field model. Certain features in the spectra of VF5 and in the force constants are related to rapid intramolecular shifting of the threefold symmetry axis in this molecule.

Vibrational Spectra of Vanadium Pentafluoride

The infrared spectrum of VF5 vapor has been studied from 140 to 4000 cm−1. The Raman spectrum has been obtained for the vapor and for the liquid at various temperatures. The spectra indicate a D3h symmetry for the molecule. Fundamental vibrational frequencies observed are: a1′, 719 and 608; a2″, 784 and 331; e′, 810, 282, and (∼200); e″, 350; all in cm−1. Approximate bond‐stretching force constants for a modified Urey—Bradley potential function are: Kr=5.51 Mdyn/A, Kd(axial)=3.94 Mdyn/A. The Raman spectra show that monomeric molecules are in low concentration in the room‐temperature liquid but constitute the main component in the liquid at temperatures above 100°C.

Heat Capacity and Other Thermodynamic Properties of MoF6 between 4° and 350°K

Thermodynamic properties of MoF6 have been measured between 4° and 350°K in order to obtain a third‐law value of the entropy for comparison with the entropy calculated from molecular data. The enthalpy change for the solid—solid transition at 263.48°±0.02°K is 1953.3±2.0 cal mole−1, and the enthalpy of fusion at the triple point, 290.73°±0.02°K, is 1034.2±1.0 cal mole−1. The vapor pressure between 291° and 320°K is represented by the equation log10 Pmm=−2047.15/T−4.28004 log10T+20.19354. At 298.15°K the enthalpy of vaporization calculated from the vapor‐pressure equation and the measured second virial coefficient, −923 cm3 mole−1, is 6630 cal mole−1. The standard entropy of the gas at 298.15°K obtained from the thermal data is 83.75±0.10 cal deg−1·mole−1. This agrees with the value of 83.77 cal deg−1·mole−1 calculated from Nazarians electron‐diffraction measurement of the Mo–F distance (1.840 A) and from Weinstock and Goodmans vibrational assignment. Thermodynamic functions are tabulated at selected tem...