Fluordiazadiphosphetidine. 21. Mitt. Die Photochemische Chlorierung von 2,2,2,4,4,4-Hexafluoro-1,3-diethyl (und dipropyl)-1,3,2λ5,4λ5-diazadiphosphetidin und die Herstellung von 2,2,2,4,4,4-Hexafluoro-1-(cyanometyl)-3-methyl-1,3,2λ5,4λ5-diazadiphosphetidin

Summary The result of the chlorination of (CH₃CH₂NPF₃)₂ and (CH₃CH₂CH₂NPF₃)₂ with chlorine under UV-radiation were the new compounds CH₃CH₂(NPF₃)₂CH₂CH₂Cl and CH₃CH₂CH₂(NPF₃)₂CH₂CH₂CH₂Cl. The reaction of CH₃(NPF₃)₂CH₂Cl with KCN and crown-ether gave the new compound CH₃(NPF₃)₂CH₂CN.

     

Fluordiazadiphosphetidine, 23. Mitt.: Die Herstellung neuer unsymmetrisch substituierter Fluordiazadiphosphetidine

Summary Using 1-chloromethyl-2,2,2,4,4,4-hexafluoro-3-methyl-1,3,2⁵,4⁵-diazadiphosphetidine as starting material for nucleophilic reactions, the following new compounds were prepared: 2,2,2,4,4-pentafluoro-4-methoxy-1-propyl-3-methyl-1,3,2⁵,4⁵-diazadiphosphetidine, 1-benzyl-2,2,2,4,4-pentafluoro-4-methoxy-3-methyl-1,3,2⁵,4⁵-diazadiphosphetidine, and 1-benzyl-2,2,2,4,4-pentafluoro-4-methylamino-3-methyl-1,3,2⁵,4⁵-diazadiphosphetidine

     

Photoemission and band structure of crystalline and amorphous iron phosphoborides

The electronic structure of some crystalline and amorphous iron phosphobirdes is investigated by the photoemission technique : XPS and UPS. For the crystalline compounds the experimental results, compared to those of pure iron, show a rearrangement of iron d states ; such results can be interpreted in a qualitative model where the low energy levels are related to the iron-metalloid bondïng levels meanwhile the upper levels are related to d iron states. For the amorphous alloys our results suggest that the electronic structure is similar to that of crystalline counterpart ; from U.V. spectra there is some hint that the slight variation of the electronic structure from crystalline Fe₃B to Fe₃P is reproduced in the amorphous alloys when the relative phosphorus concentration is increased. However, in the amorphous state the Fermi edge can be sharper and the effect of the structural disorder seems to be a broadening of the low lying states of the valence band.     

Antiferromagnetic metallic state of NiS2

The neutron diffraction experiment we have made on NiS_1.91 single crystal under increasing pressure (0<P<30 kbar) indicates a constant increase of the Néel temperature of the sample. For high pressures (P>20 kbar) and low temperatures the sample is in an antiferromagnetic metallic state as suggested by theoretical considerations for a Mott-Hubbard insulator. The pressure dependence of the second magnetic transition in NiS₂ (T = 31 K for P = 0) is also reported.     

Magnetic properties of some rare earth monoxides LnO (Ln = Pr,Nd, Sm) mixed valence state of SmO

In this paper we present the first results of magnetization measurements performed up to 40 kGauss between 1.4°K and 300°K on several Rare-Earth monoxides obtained by high-pressure synthesis. For PrO and NdO the thermal variation of the susceptibilities well agrees with a Pr³⁺ and Nd³⁺ state of the Rare Earth atoms. Such a result is in good agreement with the lattice parameter measurements. For SmO, whereas a nearly Sm³⁺ state ($\text{J =}\text{5}\text{2}$) is expected from our crystallographical and X-ray absorption data, the magnetic susceptibility is mainly temperature independent. A similar behaviour has been observed on intermediate valence compounds like SmB₆, SmS under pressure. We conclude that SmO may be also in this so-called intermediate valence state.     

XPS and UPS studies of pyrite compounds (CoX2 → CuX2, X: S; Se): Investigation of the insulator-metal transition in the NiS2−xSexsystem

We present in this paper a photoemission study (XPS and UPS) of several transition metal disulphides and diselenides (CoX₂ → CuX₂) with the pyrite structure. Our results show that all these compounds have narrow conduction bands and that the spectra for the disulphides and the diselenides are very similar. Nevertheless some changes occur in the electronic structure when going in the same series from CoX₂ → CuX₂, which are qualitatively well understood from simple theoretical considerations. Our main purpose is to discuss the influence of correlations between electrons in these narrow band systems and particularly in the case of the half-filled band (Mott-Hubbard insulator NiS₂). Considering the energy shift of the core levels deduced by XPS experiments we show that the effects of these correlations become smaller when going from CoX₂ to CuX₂, whereas they seem to remain unchanged in NiS_2?xSe_x, where an insulatormetal transition takes place. We present an attempt to quantitatively analyse our UPS results on the conduction bands. According to our results the particular behaviour corresponding to the Mott-Hubbard insulating state of NiS₂ and NiS_2?xSe_x (x < 0.5) mixed systems can be revealed by photoemission studies.     

The valence of cerium under high pressure

The valence of Ce metal shifts from 3.03 to only 3.32 (±0.02) between 0 and 120 kbar at 300 K. It is trapped by a deep minimum of the free energy which lies near valence 3.25 and is caused by strong interconfigurational mixing. In the á phase the valence is independent of pressure because of the coexistence of two crystallographic phases. The energy of promotion from Ce³⁺ to Ce⁴⁺ is found to be 1.9 eV.     

Resonant valence band satellite in palladium

Normal incidence photoemission has been used to investigate the existence of a valence band satellite as in the case of Ni. It is observed at 8.5 eV below the Fermi level and has an intensity which is only measurable when a photon energy is reached which corresponds to the threshold for excitation of an electron from the 4p levels to the Fermi level.