Röntgenographische, elektrische und spektroskopische Untersuchungen an den Palladiumchalkogeniden PdS1-xSex / Roentgenographic, Electrical and Spectroscopic Investigations of the Palladium Chalcogenides PdS1-xSex

Silvery reflecting melting cakes of PdS1-xSex (0.0 ≤ x ≤ 1.0) have been prepared by annealing mixtures of Pd, S and Se at 873 K in evacuated quartz tubes. The PdS-type mixed crystals are stable only in the ranges 0.0 ≤ .x ≤ 0.2 and 0.9 ≤ x ≤ 1.0, whereas a new phase appears in the intermediate region. The new phase PdS1-xSex (0.2 < x < 0.9) crystallizes in the space group P42/mbc and Z = 24. Lattice constants are a = 1126.2(7), c = 683.2(7) pm (PdS0.6Se0.4) and a = 1130.8(9), c = 685.4(8) pm (PdS0.4Se0.6). The relationships between the new structure type and the PtS and PdS structure types are discussed.The infrared reflection spectra of polycrystalline samples of PdS were measured between 10 and 300 K in the frequency range from 30 to 400 cm-1. Both phonons and plasmons contribute to the spectra. The temperature dependence of the plasmon contribution shows an unusual behaviour which is explained by the assumption of a phonon assisted hopping conductivity mechanism at low temperatures and a Drude-like transport at high temperatures. The normal mode which may be involved in the hopping process is proposed from a normal coordinate calculation using a three-parameter short range valence force field model. The electrical transport data are in general agreement with the optical ones. The infrared spectra of the mixed crystals PdS1-xSex (0.2 < x ≤ 1) are discussed.

Semiempirical Calculation of the Rotational Barrier and Valence Force Constants in Fluorocarbonylsulfenyl Chloride

The rotational barrier about the C-S bond in fluorocarbonylsulfenyl chloride [FC(O)SCl] is investigated using the CNDO method. The results confirm the existence of planar eis and trans conformers and the higher stability of the latter, as suggested by previous vibrational results. The valence force constants in FC(O)SCl were also calculated and the values obtained compare favourably with results from a previous normal coordinate calculation and with those of related compounds.

Raman Spectra of Gases. XXII. (CH3)3SiCl, (CD3)3SiCl and Some Normal Coordinate Calculations on (CH3)3SiNCO and (CH3)3SiNCS

The Raman spectra (0 to 3600 cm−1) of gaseous (CH3)3SiCl and (CD3)3SiCl have been recorded. It was possible to resolve the symmetric and antisymmetric SiC3 deformations. The spectra are discussed in detail and previous vibrational assignments are compared. A normal coordinate calculation has been carried out utilizing a modified simple valence force field. The extent of the vibrational coupling has been determined. It is believed that the main force constants should be transferable to other substituted trimethylsilyl compounds and this transferability is demonstrated by some normal coordinate calculations for trimethylsilylisocyanate and trimethylsilylisothiocyanate.

The Infrared and Raman Spectra of Dimethyliodoarsine

The infrared and laser–Raman spectra of liquid dimethyliodoarsine, (CH3)2AsI, have been recorded. Assignments of the observed frequencies have been made to the 24 normal modes of vibration of the molecule. A normal coordinate calculation has been carried out in support of the assignment.