Browsing by Subject "Inorganic Chemistry"

Now showing 1 - 13 of 13
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    The effects of metal ion and ligand substitution on the spectroscopic properties of metal complexes.
    (1975) Johnson, Peter Robin; Thornton, David A
    Metal-nitrogen stretching vibrations in Co(II), Ni(II), Cu(II) and Zn(II) chloride 4-methylaniline complexes are assigned by ¹⁵N-labelling in conjunction with a consideration of the relative crystal field stabilizition energies of the metal ions. Bands in the ultraviolet electronic spectra of Cu(II) β-ketoenolate complexes are more conclusively assigned by comparison of the spectra of the β-ketoenolates, their sodium salts and the copper complexes. The effect of ligand substitution on the infrared spectra of Cu(II) benzoylacetanilide complexes and their methanol adducts is used to assign copper-oxygen stretching frequencies. The effect of ligand substitution on the ultraviolet electronic spectra is used to estimate the extent of π-interaction in these complexes. The infrared spectra of six ¹⁵N-labelled Co(II), Ni(II), Cu(II) and Zn(II) N-salicylideneanthranilate complexes yield assignments of metal-ligand and certain ligand vibrations. These assignments are supported by observing the effects of metal ion and ligand substitution on the spectra. The shifts observed in the metal-ligand stretching frequencies are related to the relative crystal field stabilization energies of the metal ions and to the electron releasing and withdrawing capacities of the ligand substituents. Assignments of metal-ligand vibrations in the infrared spectra of Ni(II) and Cu(II) benzoylbenzilidenehydrazone complexes and Co(II), Ni(II), Cu(II) and Zn(II) benzoylsalicylidenehydrazone complexes are made by observing the effects of metal ion and ligand substitution on the spectra. The infrared spectra of three ¹⁵N-labelled Ni(II), Co(II) and Cu(II) triarylformazan complexes yield assignments of metal-ligand and certain ligand vibrations. The effect of ligand substitution on the infrared spectra of Ni(II) triarylformazan complexes is related to the electron releasing or withdrawing capacities of the substituents. A total of 168 complexes, of which 131 have not previously been reported, has been synthesized and discussed.
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    Heavy metal interactions with nucleic acid derivatives : a nuclear magnetic resonance study
    (1979) Koch, Klaus R; Fazakerley, G V
    The aqueous solution conformation of SAH and SAM has been investigated using lanthanide probes. SAH at pH 7.0 interacts normally with lanthanide aquo ions and lanthanide-EDTA complexes via coordination at the carboxyl group. The conformation of the homocysteine fragment is found to, be extended but bent back towards the adenine base. SAM does not interact with lanthanide aquo ions in the pH region 2-7. It does form complexes with lanthanide-EDTA species via an ion-pairing mechanism rather than direct coordination. In addition to lanthanide probes, 250 MHz 1H n.m.r. spectra yielded vicinal JHH coupling constants from which the ribose conformation in both SAM and SAH could be more accurately determined.
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    An investigation into the synthesis and structure of some pentamethylcyclopentadienyl complexes of molybdenum, tungsten and iron
    (1984) Stretch, Phillippa Moira; Moss, John R
    The extensive series of cyclopentadienyl transition metal complexes known, has made of interest the corresponding chemistry of pentamethylcyclopentadienyl transition metal derivatives, and other substituted cyclopentdienyl species. In the study two synthetic routes are described for the synthesis of new halomethyl complexes of molybdenum, tungsten and iron.
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    Isotopic labelling : application to band assignments in the infrared spectra of metal complexes
    (1978) Rutherford, Phillip Edgar; Thornton, David A
    The technique of isotopic labelling is discussed in relation to its application to band assignments in the infrared spectra of metal complexes. ¹⁵N- and ²H-labelling are applied to three classes of transition metal coordination compounds.
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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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    Isotopic labelling applied to the infrared spectra of metal complexes
    (1979) Hodgson, John Betton; Thornton, David A; Percy, G C
    An investigation of a series of imidazole complexes of first transition metal (II) nitrates, perchlorates and halides is reported. Deuteration of the imidazole ring provides reliable assignments for the internal vibrations of imidazole. This technique also permits unambiguous assignments of the internal vibrations of nitrate or perchlorate by their lack of deutero-sensitivity. The infrared spectra of imidazole and its complexes are examined in order to determine the ratio vD/ vH for bands as signed to the C-H, N-H and ring modes of the heterocyclic ring. With very few exceptions, vD/vH falls within the ranges 0. 74 to 0. 84 and 0. 93 to 1. 00 for C-H and ring vibrations, respectively. The potential usefulness of the results is discussed. Assignments of the M-N and M-halide vibrations are based on the results of the deuteration studies, metal ion substitution and on halogen substitution. The number of M-L vibrations in the far-infrared satisfies the selection rules for the molecular point or site group symmetries and facilitates accurate structural assignments.
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    Isotopic labelling applied to the infrared spectra of metal complexes
    (1977) Engelter, Carola; Thornton, David A
    The infrared spectra of pyridine adducts of first transition series metal(II) acetylacetonates are discussed in relation to the band shifts induced by ¹⁵N-labelling and deuteration of the pyridine ring and by metal ion substitution. ¹⁵N-Labelling aids in establishing the pyridine ring vibrations, while deuteration and metal substitution are more useful in assigning the νM-L frequencies. Results of the isotopic labelling study lead to a revision of previously-reported νM-O and vC---O frequencies. This technique also facilitates assignment of the νM-N vibrations, observed in the region below 200 cm⁻¹. The occurrence of these bands in this spectral region was expected because of the known relative weakness of the M-N bond strength in pyridine adducts. The effects on the spectra resulting from introduction of a variety of substituents into the pyridine ring are discussed on the basis of the electronic effects of the substituents. After allowing for mass effects, electron-withdrawing substituents are found to decrease νNi-N frequencies while electron-releasing substituents exert negligible effect on the νNi-N bands. An opposite trend is, however, observed for the νNi-O bands and is explained. An investigation of a series of aniline and p-toluidine complexes of first transition metal(II) isothiocyanates is reported.
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    Metal-ions in biofluids-aluminium in-vitro studies
    (1986) Qubeka, Kuku V V
    [Page ii missing] The stoichiometric stability constants of aluminium III of inorganic phosphates and adenine nucleotides have been determined at ionic strength. I = 0,15 and a temperature of 25°C using glass electrode potentiometry and computer modelling. The protonation sequence for tripolyphosphate has been determined using n.m.r. studies.
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    A spectroscopic study of square planar platinum (2) complexes
    (1983) Hall, Philip Simon; Thornton, David A; Foulds, Gary André
    A number of spectroscopic techniques consisting of ultraviolet, ¹H-NMR and mass spectrometry have been used in the structural analysis of square planar Pt(II) complexes. The complexes trans-[PtBr₂(Y) (R-an)] (Y = C₂H₄,CO; R-an = substituted aniline) were prepared and investigated by the spectrosopic techniques. Infrared assignments were aided by isotopic labelling studies. The discussion of the two series of complexes are based on their relation to one another. The complexes trans-[PtX₂ (CO) (L)] (X = Cl, Br; L = aniline, pyridine N-oxide, pyridine, ammonia, imidazole and pyrazole) were prepared from their corresponding ethylene analogues. Infrared assignments, with labelling studies, are given for the complexes. The bonding effects in these complexes were studied using ¹H-NMR and ultraviolet spectroscopy. The ¹H-NMR spectra reveal that there is a fluxional behaviour of the ligands in some of the complexes. Hence, cold temperature studies were required to "freeze out" this fluxional behaviour and observe the expected signals due to the ¹⁹⁵pt-H coupling. The electronic effects are different when the ligand, L, was capable of forming σ-bonds with Pt²+, compared to when L was capable of forming both a- and π-bonds with Pt²+. The mass spectra show the M+ peak and subsequent fragmentation in the complexes. The fluxional behaviour of imidazole in trans-[PtX₂(C₂H₄) (Him)] was monitored by cold temperature studies. Using band shape analysis (with the aid of a computer) the activation paramaters for the exchange processes were determined. The dependence of the imidazole proton signals on temperature, solvent and excess ligand, all indicate that an intermolecular exchange process is occurring. Studies on the complex trans-[PtX₂(C₂H₄) (pyz)] and the effect of solvent on the complexes are being pursued, and it is hoped that an understanding of the role of the solvent in the exchange process will become apparent.
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    A spectroscopic study of square planar platinum (II) complexes
    (1982) Foulds, Gary André; Thornton, David A
    A number of spectroscopic techniques consisting of infrared, Raman ultraviolet and 1H-nmr spectroscopy have been used in the structural analysis of square planar Pt(II) complexes.
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    A spectroscopic study of square planar rhodium(I) complexes
    (1989) Hall, Philip Simon; Jackson, Graham Ellis; Moss, John R; Thornton, David A
    Ninety square planar Rh(I) complexes of the type cis-[Rh(CO)₂(X)(L)], [Rh(COD)(X)(L)], [Rh(CO)₂(L)₂]ClO₄ and [Rh(COD)(L)₂]ClO₄ (X is Cl or Br; COD is 1,5-cyclooctadiene; L is aniline, pyridine, pyridine N-oxide, imidazole and ammonia), as well as their isotopically labelled derivatives (¹³CO, ²H and ¹⁵N) were prepared, characterized by microanalysis and melting point, and investigated by the following spectroscopic techniques: infrared, Raman, ultraviolet, mass spectrometry, and 1H, ¹³C and ¹⁵N nmr spectroscopy. The comprehensive isotopic labelling studies allowed unambiguous assignment of the infrared modes in the 4000-50 cm⁻¹ region. The infrared assignments are discussed with reference to their vᴰ/Vᴴ ratios, the various ligands and halogens used, the charges on the complexes, and are compared to similar compounds. The 1H, ¹³C and ¹⁵N nmr runs were performed at room and low temperatures. Fluxionality of the ligands (L) was observed and the exchange process was monitored by variable temperature nmr. The enthalpy and entropy values for the intermolecular exchange of L in the complexes cis-[Rh(CO)₂(X)(L)] were obtained by a complete computer simulated band shape analysis of the carbonyl region of the ¹³C nmr spectra. The non-equivalence, and specific assignment of the carbonyl groups in the cis- [ Rh(CO)₂(X)(L)] complexes were determined by recording the variable temperature ¹³C nmr spectra of the doubly enriched species cis[Rh(¹³CO)₂(X)(¹⁵N-ligand)]. ²J(¹³C-Rh-¹⁵N) values are reported for the first time. The ¹J(¹⁵N-¹⁰³Rh) coupling constants are rationalized in terms of the metal-nitrogen bonding, and correlate with the s-character of the bonding electron on nitrogen. While the solution electronic spectra reveal that the complexes are discrete monomeric entities in solution, there are indications of metal-metal interactions in the solid-state. The normal coordinate analysis study of the complexes cis-[Rh(CO)₂(X)(L)] involved the calculation of a general valence force field by applying the eigenvector method of Becher and Mattes. The results show that point-mass-modelling and simplified force field, as assumed in our treatment, describes, to a good approximation, the vibrational properties of the complexes. The potential energy distribution provided further support for the proposed infrared assignments of the complexes.
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    The synthesis and reactivity of functionalised alkyl transition metal complexes
    (1990) Friedrich, Holger Bernhard; Moss, John R
    The complexes [CpFe(CO)₂CH₂X] and [CpW(CO)₃CH₂X] (Cp = n⁵-C₅H₅; X=Cl, Br, I) have been prepared and their reactivity with a series of tertiary phosphines, amines, SMe₂ and AsPh₃ in THF, CH₃CN and MeOH has been investigated. Two types of cationic products, namely the ylide complexes [CpM(CO)nCH₂L]+ or the disubstituted complexes [CpML₂(CO)n-l]+ (M = Fe, n = 2; M = W, n = 3) were obtained, depending on the halide (X), the ligand (L), the metal (M) and the solvent used. The variables X, L, M and the solvent used were also all found to influence the rates of the reactions. Thus the relative reaction rates of the complexes [CpFe(CO)₂CH₂Br] and [CpW(CO)₃CH₂Br] with L were determined by 1 H NMR spectroscopy and found to increase with increasing pKa and decreasing cone angle of L. In general, the rate of reaction of [CpFe(CO)₂CH₂X] and [CpW(CO)₃CH₂X] with L increases in the sequence Cl < Br < l and the reactions of [CpFe(CO)₂CH₂X] with L are significantly faster than the corresponding reactions of [CpW(CO)₃CH₂X]. The reactions of [CpFe(CO)₂CH₂Br] and [CpW(CO)₃CH₂Br] with dppe {dppe = bis(diphenylphosphino)ethane} yield the bridged dicationic ylide complexes [{Cp(CO)₂FeCH₂}₂{PPh₂(CH₂)₂PPh₂}] and [{Cp(CO)₃WCH₂}₂{PPh₂(CH₂)₂PPh₂}] respectively.
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    Synthetic and structural investigation into homo- and hetero-, di- and tri-nuclear complexes containing osmium
    (1986) Sutton, Elizabeth Eldred; Moss, John R
    Chain cluster complexes have been largely neglected in the general discussion on metal cluster complexes. The first chapter of this thesis has been devoted to an updated review of the synthetic and structural aspects of chain cluster complexes, classifying species of this type in a group of their own, as a sub - set of the large class of compounds loosely referred to as metal cluster complexes. The reaction of Os₃(CO)₁₂ with X₂ (X = Cl, Br or I) in benzene, in direct, bright sunlight or a Hanovia photo-chemical reactor, has been studied. The nature of the products of the reactions depends critically on the experimental conditions employed. Os2(CO)₈X₂ (X = Br or I), among other products, are obtained in reasonable yield, directly from Os₃(CO)₁₂. (Os₂(CO)₆I₂ has been prepared from Os₂(CO)₈I₂ in 80% yield and the reactivity of the hexa-carbonyl derivative with CO, PPh₃, PMe₂Ph, I3, H₂ and C₂H₄ has been studied. The new species, Os2(CO)₆(PPh₃)₂I₂ and Os2(C0)₆(PMe₂Ph)₂I₂, are obtained. Cis-Os(CO)₄X₂ (X = Cl, Br or I) are thermally converted into Os₂(CO)₆X₄ (X = Cl, Br or I) species.