Colin H. W. Jones

Mössbauer studies of iron-bearing minerals in coal and coal ash

Abstract 57 Fe Mossbauer spectroscopy has been used to characterize the iron-bearing minerals present in some British Columbia coals. The minerals observed in a range of samples include pyrite/marcasite, siderite, jarosite, rozenite or melanterite, and Fe 2+ -bearing clay minerals such as illite. The presence of jarosite is confirmed through the magnetic hyperfine interaction observed at 4.2 K. The absence of magnetic ordering at 4.2 K for the ferrous sulphate component indicates the presence of rozenite, FeS0 4 · 4H 2 0, or melanterite, FeS0 4 · 7H 2 0, rather than szomolnokite, FeS0 4 · H 2 0 or FeS0 4 . The effects of ashing on two of the coals is also studied.

A spectroscopic investigation of some organotellurium—mercury(II) complexes

Organotellurium—mercury(II) complexes of the form R2Te·HgX2 (R = Ph, p-EtOC6H4, X = Cl, Br, I), α-Me2TeI2·HgBr2, Ph2Hg·(Me2TeI2)2, (p-EtOC6H4Te)2Hg, p-EtOC6H4Te·HgCl, R2Te2·HgX2 (R = p-EtOC6H4, X = Cl, Br, I), have been studied using 125Te Mossbauer spectroscopy and infrared and Raman spectroscopy. The spectroscopic data are interpreted in terms of possible structures for the complexes.

The preparation of di-t-butyl ditelluride and di-t-butyl telluride and the 125te NMR and Mössbauer spectra of some dialkyl tellurides and ditellurides

Abstract The synthesis of di-t-butyl ditelluride, t-Bu 2 Te 2 , and di-t-butyl telluride, t-Bu 2 Te, are reported together with that of di-(neo-hexyl) ditelluride. New syntheses of Me 2 Te 2 and i-Pr 2 Te 2 are presented. The high resolution 125 Te NMR data and the Mossbauer data for these compounds are discussed. The use of tellurium-proton couplings in high resolution 125 Te NMR spectra in assigning the resonances in mixed dialkyl ditellurides is also illustrated.

Magnetic properties of nanocrystalline iron oxide/amorphous manganese oxide nanocomposite thin films prepared via photochemical metal-organic deposition

Maghemite (γ-Fe2O3) nanocrystals have been prepared by the thermal decomposition of metal-organic precursors in the presence of oleic acid. These nanocrystals were characterized by transmission electron microscopy, SQUID magnetometry, and Mossbauer spectroscopy. Samples of maghemite nanocrystals with a median diameter of 4 nm were found to be superparamagnetic, with a blocking temperature of ca. 36 K. These nanocrystals were encapsulated in an amorphous manganese oxide matrix by means of photochemical metal-organic deposition. In this process, solutions containing γ-Fe2O3 nanocrystals and manganese(II) 2-ethylhexanoate were spin coated on silicon substrates. Upon irradiation, the photosensitive manganese precursor undergoes decomposition, leaving a manganese oxide thin film containing dispersed nanocrystals. Photoresist-free lithographic deposition of micron-sized features composed of the γ-Fe2O3 nanocrystals/amorphous manganese oxide nanocomposite was carried out. The magnetic properties of the nanocomposite thin films were measured, and shown to bear differences with the bulk nanocrystals. In particular, the blocking temperature is lowered with increased nanocrystal dilution. The magnetic properties of the system are discussed in terms of clusters of strongly interacting superparamagnetic nanocrystals.

Aspects of the Chemistry of Diarylditellurides and Related Compounds containing Telurium to Tin Bonds

The examination mixtures of two ditellurides by mass and 1H nmr spectroscopies provides the first evidence for the existence of unsymmetrical diarylditellurides, RTeTeR′. Possible mechanisms for the redistribution reaction are discussed and it is noted that no positive support for a radical mechanism is obtained. Appearance potential measurements on the ion (aryl)Te+ derived from a number of organotellurium compounds suggest that tellurium extrusion may be a low energy pathway for the decomposition of diarylditellurides. A new series of compounds, Ph3SnTe(aryl) is reported and they are examined by 119Sn and 125Te Mosabauer spectroscopies. Attempts are made to interpret the Mosabauer data in terms of orbital populations, and it is demonstrated that only an sp bonding model gives a self-consistent interpretation of the combined tin and tellurium Mosabauer data.

125Te Mössbauer spectra of the Te (IV) oxides and oxyfluorides

The 125Te Mossbauer spectra for a number of Te(IV) oxides are reported in which the tellurium is present in either a distorted trigonal bipyramidal or distorted tetrahedral coordination with the lone-pair occupying one of the coordinate positions. The isomer shifts and quadrupole splittings are interpreted in terms of the relative s and p character of the stereochemically active lone-pair. Mossbauer data for KTeF5, K2TeO2F2, Cs2TeO2F2, and Cs2TeOF4 are also presented and discussed.

Tellurium-125 Mössbauer and NMR data for tetraphenyltellurium and bis(2,2'-biphenylylene)tellurium

Abstract The 125Te solution NMR chemical shifts of Ph4Te (508.9 ppm) and (C12H8)2Te (486.3 ppm) have been measured at ambient temperature, together with the 125Te Mossbauer parameters for the neat solids: Ph4Te (δ 0.09, Δ 5.60 mm s−1, (C12H8)2Te (δ 0.42, Δ 6.40 mm s−1) at 4.2 K. These results are compared with those for other organotellurium compounds. The mass spectra of these compounds are also reported.

The reaction of trimethylchlorosilane with phenyltelluromagnesium bromide in tetrahydrofuran: Characterisation of the products by 29Si and 125Te NMR spectroscopy

Abstract The products of the reaction of Me 3 SiCl with PhTeMgBr in THF have been identified with the aid of high resolution 29 Si and 129 Te NMR spectroscopy. In addition to the expected product Me 2 SiTePh (40%), the symmetrical telluride (Me 3 Si) 2 Te (10%) and the ether Me 3 SiO(CH 2 ) 4 TePh (45%) are also formed. The latter results from ring-opening of the solvent THF by Me 3 SiCl followed by reaction of the product with PhTeMgBr.

Cyclo-1,4-dimethylenetetratellurium

Abstract The mass spectrum and the Mossbauer spectrum provide evidence that the compound regarded previously as ditelluromethane, CH 2 Te 2 , is cyclo-1,4-dimethylenetetratellurium, C 2 H 4 Te 4 .

Donor–acceptor complexes of organotellurium compounds. Physical studies: tellurium-125 Mössbauer spectroscopy for the measure of charge transfer. Crystal and molecular structure of the complex dibenzotellurophene–7,7,8,8-tetracyano-p-quinodimethane

A range of organotellurium(II) compounds, together with two selenium compounds are used as donors to form donor–acceptor complexes with 7,7,8,8-tetracyano-p-quinodimethane (tcnq). Generally, the stoicheiometry is 1 : 1 but two ditellurides provide an exception in giving R2Te2·2tcnq (R = Ph or C6H4OEt-p). The complexes are electrical insulators although the conductivities vary over several orders of magnitude. The two ditelluride complexes show evidence of semiconducting properties. E.s.r. and i.r. data are discussed and it is concluded that in most cases the degree of charge transfer is small. Exceptions to the rule appear to be the tcnq complex of 1,3-dihydro-2-telluraindene and Ph2Te2·2tcnq which do involve significant charge transfer as assessed from a 125Te Mossbauer study. A method of assessing the degree of charge transfer for donor–acceptor complexes of organotellurium compounds using Mossbauer spectroscopy is given. The crystal and molecular structure of the tcnq complex of dibenzotellurophene has been determined and molecular parameters compared with the known structures of the component molecules. The structural data confirm conclusions from i.r. and Mossbauer studies that, in this instance, the degree of charge transfer is very small. A novel feature of the structure is that in addition to intermolecular interactions within the mixed stacks, there are significant Te ⋯ N interactions between stacks. As a consequence, two different orientations of tcnq occur in the complex.