Browsing by Author "Niven, Margaret Lilian"

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    Isotopic labelling applied to the infrared spectra of metal complexes
    (1980) Niven, Margaret Lilian; Percy, G C; Thornton, David A
    An ir investigation of a series of 2-aminomethylpyridine complexes of first transition metal(II) perchlorates, tetrafluoroborates, halides and thiocyanates is reported. Comparisons with the spectra of related complexes of 2,2'-bipyridine and ethylenediamine together with metal-ion substitution, deuteration and ¹⁵N isotopic labelling of the amino group in 2-aminomethylpyridine enable reliable band assignments to be made. The study shows that in complexes of the type M(amp)nX₂, metal-to-amino-nitrogen stretches occur at frequencies greater than 350 cm⁻¹ , while the metal-to-pyridine-nitrogen stretches are generally below 300 cm⁻¹, the assignment of the latter being generally complicated by the presence of metal-to-halogen vibrations. In addition to an x-ray crystallographic investigation of the complex [Ni(amp)₃](BF₃ ₄)₂, considerable structural information about these complexes is obtained from correlations between the number of M-L vibrations observed in the far ir and those predicted for localized molecular point symmetries on a group theoretical basis.
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    A study of secondary bonding effects in Werner clathrates
    (1988) Suckling, Adrian Philip; Nassimbeni, Luigi R; Niven, Margaret Lilian
    The crystal structures of Ni(NCS)₂(4-ViPy)₂.nG where nG = 2CH₂Cl₂ (I), 2CCl₄ (II), 1.8CH₂I₂ (III) and CHI₃ (IV), as well as the crystal structure of [Ni(NCS)₂(4-ViPy)₄]. [Ni(NCS)₂(4-ViPy)₃(thf)].2CHI₃ (V) have been elucidated. The diiodomethane guest molecules in STRUCTURE III were severely disordered at room temperature and so this structure was solved at -40°C. The dichloromethane clathrate is isomorphous with the chloroform clathrate of the same host, and both these clathrates have a similar packing to the carbon tetrachloride clathrate. There is significant secondary bonding between the sulphur (donor) of the isothiocyanate ligand of the host and the iodines (acceptor) of the halogenated guest molecules in compounds III, IV and V. The iodoform clathrates, compounds IV and V, also show strong similarities in their packings. Particular attention has been paid to the shape and size of the cavities in which the guest molecules find themselves, in order to gain a better understanding of the nature of these clathrates. This has also shed some light on the probable cause of the disordered diiodomethane molecules in STRUCTURE III. Packing densities and volume comparisons of the [Ni(NCS)₂(4-ViPy)₂] clathrates have been carried out. Solid - state U.V/visible spectroscopy was used to obtain information on the host conformation, and thermal analysis (thermogravimatry and differential thermal analysis) was used to obtain insight into the host - guest interactions of these clathrates.
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    Werner clathrates with potential chiral selectivity : preliminary investigations
    (1985) Zemke, Klaus Jürgen; Niven, Margaret Lilian; Nassimbeni, Luigi R
    The structures of the Werner clathrate Ni(NCS)₂(α-phenylethylamine)₄, as host complex made from enantiomerically pure amine ligand and from the racemic mixture, as well as its clathrate with sec-butylbenzene have been determined by x-ray diffraction.