Chemical Studies of Complex Formation and Speciation: An Investigation of Selected Tellurium, Gallium, and Antimony Systems

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dc.contributor.advisor Taylor, Michael J. en Baker, Lisa-Jane en 2007-07-13T07:31:23Z en 2007-07-13T07:31:23Z en 1994 en
dc.identifier THESIS 95-187 en
dc.identifier.citation Thesis (PhD--Chemistry)--University of Auckland, 1994 en
dc.identifier.uri en
dc.description Full text is available to authenticated members of The University of Auckland only. en
dc.description.abstract Raman spectra of aqueous and extracted phases of solutions of Te(IV) in HCI show that the hexahalotellurate(IV) anion predominates at high acid concentrations. At lower concentrations the evidence points to the presence of a second species, TeCl4 (OH)-. 125Te NMR of aqueous solutions with HCL concentrations of less than 7 mol L-1 indicate a third species is present, which may be TeCl2(OH)2. 125Te NMR of the extracted phases of these lower HCL concentrated solutions can be accounted for in terms of a single species only, namely TeCl4(OH)- Te(IV) in HBr solutions showed little evidence for the formation of any species other than TeBr 62-. The crystal structure of [t-BuNH3]2TeBr6 is presented as an example of a compound in which the anion is appreciably distorted from regular octahedral symmetry. The resultant lower symmetry is reflected in the vibrational spectra, which has only been noted once before' Two other compounds are presented which also demonstrate this spectroscopic phenomenon, namely the diaminopropane derivatives of hexachlorotellurate(IV) and hexabromotellurate(IV). As with [t-BuNH3] 2TeBr6, (dapH2)TeCl6 has been shown to contain a distorted anion in the solid state. These distortions can be accounted for by hydrogen bonding between the cation and anion. 71Ga NMR spectroscopy has been used to examine Ga(III) in aqueous solutions which also contain halide and thiocyanate ligands. The existence of gallium mixed aqua-halo complexes was investigated in non-aqueous solution (as an extracted phase in either diethyl ether or methyl isobutyl ketone(MIBK)). The 71Ga NMR chemical shifts of all 35 possible four-coordinate Ga(III) species containing Cl-,Br-, I- and/or NCS- were found, including the anion with four different ligands, [GaCIBrI(NCS)]-. The speciation of gallium in aqueous and non-aqueous solution with only thiocyanare was studied. In aqueous solution no limiting value for a single Ga(III) species with only thiocyanate ligands was found. Extraction into diethyl ether or MIBK yielded almost exclusively [Ga(NCS)4]-. The 13C and 14N NMR chemical shifts are given for this species. The latter nucleus was also used in the characterisation of the species [GaX4-n (NCS)n]-, where X = Cl, Br, or I, and n = 1 - 4. For some of the chloride-containing species in this series the coupling constant 1J(Ga-N) was observed in both 71Ga and 14N NMR spectra. The replacement of an anionic ligand by a neutral solvent molecule bonded to Ga(III) can result in neutral etherates, e.g. GaI3.Et2 O, or analogous THF adducts, GaI3-THF. The chemical shifts of GdXn Y3-n-Et2O(X and Y = Cl, Br, or I; n = 0 to 3), and a number of anaiogous THF adducts have been found. Adducts of GaI3 with neutral Group 15 donor ligands have been investigated using a range of nitrogen, phosphorus, arsenic, antimony, and bismuth compounds. Four nitrogen donor ligands formed adducts, which are characterised by 71Ga NMR chemical shifts. Triphenylphosphine formed a 1:1 adduct, ph3pGaI3, which crystallised from ether. The vibrational spectra are reported as well as the X-ray crystal structure. Triphenylarsine produced two solids when reacted with GaI3.Et2 O. The 1:1 adduct Ph3AsGaI3, is isomorphous and isostructural with the phosphine analogue. The second compound is [Ph3AsI][GaI4]. The x-ray crystal structures and vibrational spectra of both arsenic-containing compounds are reported. The products of the reactions of triphenylstibine with molecular bromine or iodine in a number of organic solvents have been examined in the solid state by X-ray diffraction, infrared and Raman spectroscopy, and in solution by NMR. In addition to the dihalides, Ph3SbX2, oxo-bridged compounds, (Ph3SbX)2O, have been obtained. Vibrational assignments are made for (ph3SbX)2O, where X=Br and I, and the crystal structure of the latter is also presented. These species are also characterised by NMR; their 13C and 1H parameters being the first report of such. Bromo- and iodotetraphenylantimony(V) have been investigated. If we formulate dihalotriphenylantimony(V) as Ph3SbXY, where X=Y=Br or I, then the oxo-bridged compounds are the case where X=Br or I, and Y=OSbPh3X. The tetraphenylantimony halides are thus X=Br or I, and Y=Ph, and so form a natural extension of the series. These have been studied by the spectroscopic methods mentioned above, and the X-ray crystal structure of the iodide has been determined. This facilitates a new assignment of the vibrational spectra. The question of the solution behaviour is also addressed through multinuclear NMR spectroscopy, including 121Sb NMR. en
dc.language.iso en en
dc.publisher ResearchSpace@Auckland en
dc.relation.ispartof PhD Thesis - University of Auckland en
dc.relation.isreferencedby UoA9957834514002091 en
dc.rights Restricted Item. Available to authenticated members of The University of Auckland. en
dc.rights Items in ResearchSpace are protected by copyright, with all rights reserved, unless otherwise indicated. en
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dc.title Chemical Studies of Complex Formation and Speciation: An Investigation of Selected Tellurium, Gallium, and Antimony Systems en
dc.type Thesis en Chemistry en The University of Auckland en Doctoral en PhD en
dc.rights.holder Copyright: The author en

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