Resonant Raman scattering from screened longitudinal optical phonons in EuTe

Forbidden resonant Raman scattering from screened longitudinal optical, LO, phonons has been observed in the back-reflection geometry from n-type EuTe at 2°K. The Raman shift increased with increasing excitation frequency but was always between the LO and TO phonon frequencies. This effect is explained in terms of a varying ‘effective’ carrier concentration as a function of laser penetration depth through the surface depletion layer in the situation of large phonon wave vector. Conduction band and lattice parameters have been calculated from infrared Reststrahlen and plasma edge measurements.     

Infrared dielectric dispersion of ZnGeP2 and CdGeP2

The polarised i.r. reflectivity spectra of single crystals of the non-linear chalcopyrite materials ZnGeP₂ and CdGeP₂ have been measured over the spectral range 40–700 cm^?1. Analysis of the spectra using classical dispersion theory and the Kramers-Krönig technique has yielded, in each material, five modes with frequencies between 80 and 385 cm^?1 with the polarisation perpendicular to the optic axis. Parallel to the optic axis, two modes have been observed with frequencies between 300 and 400 cm^?1. The phonon dispersion curves of the isoelectronic analogue GaP have been used, together with a group theoretical analysis, to assign specific atomic displacements to the observed modes.     

The coordination chemistry of simple phospholes. Complexes of rhenium,ruthenium, cobalt,rhodium and iridium chlorides and of some chlorocarbonyls of ruthenium and rhodium

The reactions of 1-phenylphosphole (PP), 3-methyl-1-phenylphosphole (mPP), 3,4-dimethyl-1-phenylphosphole (dPP) and, in certain instances, 1-n-butyl-3,4-dimethylphosphole (dBP) with some transition metal chlorides and some metal-Cl-CO systems are reported. These reactions show that simple phospholes in general unexpectedly behave much like ordinary tertiary phosphines and that, unlike the reactions with Ni(II), Pd(II) and Pt(II), the complexes formed are conventional in most respects. However, a few unusual reactions were observed. For example, mPP partially reduces Ru(III) to give a mixed-valent Ru(III)-Ru(II) complex while PP reduces Ir(III) to Ir(I). From infrared spectroscopic studies of the square-planar Rh(I) complexes L₂Rh(CO) Cl (L = phosphole), it appears that donor character decreases with decreasing substitution on the phosphole ring carbon atoms. Phosphorus-phenyl cleavage has been observed in reactions of 1-phenylphosphole with Rh-CO systems. The results are briefly discussed in relation to the behaviour of other phospholes in similar reactions and in the context of the electronic structure of phospholes.     

The synthesis and some NMR properties of 2,3-bis(diphenylphosphino)-6-phenyl-λ3-phosphinine

The synthesis, from 1,2,5-triphenylphosphole and bis(diphenylphosphino)acetylene, of 2,3-bis(diphenylphosphino)-6-phenyl-λ³-phosphinine, the first example of a λ³-phosphinine bearing phosphorus-containing side chains, is reported. This compound shows in its nmr spectrum the largest value of ³J_pp (178 Hz) yet reported for a system containing the P^III-C-C-P^III linkage. Evidence is presented which supports the idea that this extraordinarily large coupling arises as a result of geometrical factors which place the non-bonding electron pairs of the two side-chain P atoms in very close proximity to one another. Reactions of the λ³-phos-phinine with Ni(II) and Pt(II) compounds are briefly discussed in the context of the nmr properties of both the ligand and the complexes formed.     

Mössbauer effect in synthetic analogs of rubredoxin

Mössbauer measurements have been performed on three recently synthesized Fe(II) complexes with tetrahedral sulphur coordination, simulating the active center in reduced rubredoxin. One of the complexes has virtually identical Mössbauer parameters with reduced rubredoxin.     

High-frequency-pass metallic mesh interference filters

Summary High-efficiency metallic mesh high-frequency-pass interference filters have been designed and constructed for the wavenumber region 30100 cm^–1. Widebandpass filters have been fabricated using a combination of highpass and lowpass filters. The highpass filters have performed successfully at low temperatures.     

Bis(diphenylphosphino)Alkane / Co(II)/Tetrahydroborate and Cyanotrihydroborate Reactions: Formation of Unusual Bis(diphenylphosphino)methane Complexes and the Influence of Carbon Monoxide

Abstract

Reactions between Co(II), bis(diphenylphosphino)methane (dppm) and either NaBH₄ or NaBH₃CN have been studied. They follow pathways which are in marked contrast to those followed by Ph₂P(CH₂)nPPh₂ (n=2?6) in the presence of NaBH₄ in which the final product is normally CoH(phosphine)₂ although binuclear BH₄-bridged complexes may sometimes be obtained. The products obtained with dppm are Co₂X₃(dppm)₂ (X=Cl,Br) (I), CoCl(dppm)₃ (II), {CoHX(dppm)₂}Y (X=Cl, Br, I, BH₃CN; Y=Cl,BH₃CN,BPh₄,Clo₄) (III), and Co₂H₂(dppm)₃ (IV). While a binuclear A-frame structure can be proposed for the Co(I)-Co(II) species (I), crystal twinning has so far prevented an X-ray determination. However, X-ray studies on (II) and (IV) have shown that (II) contains tetrahedral Co(I) to which one chloro and three monodentate dppm ligands are attracted while (IV) is a binuclear species containing bridging dppm ligands and two terminal hydrides. The compounds (III) are octahedral Co(III) complexes. Possible mechanisms for the formation of these in strongly reducing environments will be discussed.