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Item The interaction of group 15 and 16 donor ligands with the later transition metals : a collection of published papers presented in application for the degree of Doctor of Science at Massey University(Massey University, 1999) Brodie, Andrew MThe scientific publications contained in this thesis are the results of approximately 30 years of transition metal chemistry research, mainly pursued at Massey University. The emphasis has been on the synthesis of interesting new compounds and their subsequent characterisation using a variety of physicochemical techniques. Where appropriate reactivity studies have also been carried out on the new compounds. Chapter 1 contains papers concerned with ligands containing the Group 16 donor, sulfur, although there are a few selenium donors included. The particular ligands studied are tertiary phosphine and arsine chalcogenides, thioarmides, thioureas, thiolates and thioethers with copper and the carbonyls of Group 6 and osmium.In Chapter 2, papers detailing research into the metal binding properties of the human milk protein, lactoferrin and related small molecule systems containing phenolate donors are grouped together. A number of relevant copper thiolate systems are included in this chapter as well, which link to the paper on the blue copper protein, azurin. Finally, in this chapter, are papers describing the preparation and characterisation of a number of complexes related to the antitumour copper(II) 2-formylpyridine thiosemicarbazone system. The theme for Chapter 3 is Group 15 donor ligand complexes, in particular those of nitrogen and phosphorus. The discovery that N-phenylthiourea could be desulfurized in a reaction with copper(II) led to the investigation of phenylcyanamides as ligands. A number of tertiary phosphine ligands have been examined, including the bulky tribenzylphosphine, and research in this area is continuing. Papers with an organometallic theme form the contents of Chapter 4.Item Niobium K-Edge X-ray Absorption Spectroscopy of Doped TiO2 Produced from Ilmenite Digested in Hydrochloric Acid(American Chemical Society, 2022-08-16) Haverkamp RG; Kappen P; Sizeland KH; Wallwork KSNiobium doping of TiO2 creates a conductive material with many new energy applications. When TiO2 is precipitated from HCl solutions containing minor Nb, the Nb in solution is quantitatively deposited with the TiO2. Here, we investigate the structure of Nb doped in anatase and rutile produced from ilmenite digested in hydrochloric acid. Nb K-edge X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) are used to characterize the environment of 0.08 atom % Nb doped in TiO2. XANES shows clear structural differences between Nb-doped anatase and rutile. EXAFS for Nb demonstrates that Nb occupies a Ti site in TiO2 with no near neighbors of Nb. Hydrolysis of Ti and Nb from acid solution, followed by calcination, leads to a well dispersed doped material, with no segregation of Nb. Production of Nb-doped TiO2 by this method may be able to supply future demand for large quantities of the material and in energy applications where a low cost of production, from readily available natural resources, would be highly desirable.Item Studies on lactoferrin, a metal binding protein in human milk : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Chemistry at Massey University(Massey University, 1979) Plowman, Jeffrey ErnestLactoferrin (Lf), isolated from human colostrum, has been complexed with a variety of transition metal ions. In addition to binding two iron(III) or copper(II) ions it strongly and specifically binds two cobalt(III), chromium(III) and manganese(III) ions, in the presence of bicarbonate. Such strong, specific binding of copper(II) to lactoferrin will not occur in the absence of bicarbonate, instead only a weak interaction is observed. Lactoferrin has also been shown to weakly bind manganese(II), cobalt(II), nickel(II), zinc(II), cadmium(II), lead(II) and mercury(II), though manganese(II) will undergo aerial oxidation in the presence of the protein and bind as manganese(III). Those metal ion protein complexes have been examined using the techniques of fluorescence, electronic, e.s.r. and Resonance Raman spectroscopy. The close similarity between the spectra of the complexes Fe2Lf, Cu2Lf, Co2Lf, Mn2Lf and Cr2Lf with those of transferrin and ovotransferrin reinforce the postulate that the metal binding sites in all three proteins are similar. The sites in all three proteins are essentially rhombic in character and contain 2-3 tyrosyl residues and at least one histidyl residue. A distinct heterogeneity is evident from the e.s.r. spectrum of Cr2Lf and metal ion replacement studies indicate that chromium in one site is more labile than the other. In addition to the Specific sites lactoferrin appears to have a number of non-specific sites on the outside of the protein capable of weakly coordinating metal ions such as chromium(III) and copper(II). Differences evident in the non-specific sites available to copper when manganese(III) is bound to lactoferrin, to those available when iron(III), cobalt(III) and chromium(III) are bound, suggest that the stronger binding of manganese(III) results from it inducing a different conformational change in the protein to those other metals and one that favours the higher stability of its metal-protein complex. A series of small molecular weight complexes of iron(III) with bi-, tri-, tetra- and hexadentate ligands, containing phenolate groups were prepared and examined by electronic, e.s.r. and Mössbauer spectroscopy. Complexes of copper(II) with nitrogen bases and chloro- and bromo-substituted phenolates were prepared and examined by electronic and e.s.r. spectroscopy. Results from these studies would favour the involvement of three tyrosyl residues and two cis histidyl residues in the metal-binding sites of lacto-ferrin and from studies on the copper complexes it seems likely that one histidyl and one tyrosyl are axially coordinated to the metal. Evidence from a single crystal x-ray structure is presented which would favour the interaction of bicarbonate ion with iron(III) via a solvent (water) molecule.Item Metal coordination studies of sulphur ligands : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Chemistry at Massey University(Massey University, 1979) Larsen, Nigel GrantTransition metal complexes of ligands containing thioether sulphur have been investigated. Section I, concentrates on Cu(II) complexes, and to a lesser extent Cu(I) complexes, of mixed sulphur-nitrogen ligands. Some complexes of Co(II) and the d8 metal ions, Ni(II), Pd(II) and Pt(II), have also been included. In Section II, complexes of the Group VIB metals (Cr(c), No(C), W(C)) are discussed. SECTION I All of the complexes have been investigated using infrared and electronic spectroscopy, with electronic spectra for some of the Cu(II) complexes also being recorded at 90K. The Cu(II) complexes have also been studied using electron spin resonance (esr) spectroscopy. For a variety of solvents at 77K, esr has been especially useful in revealing the complex behaviour of some of the compounds. i) Complexes of 2-(3, 3-dimethyl-2-thiabutyl) pyridine (tbmp) The ligand has been used to prepare the Cu(II) complexes, Cu(tbmp)nX2 (n=1, X=Cl-, Br-; n=2, X=BF4-, Cl04-, Cl-, Br-), [Cu(tbmp)2X]BF4. (X=Cl-, Br-), and the Cu(I) complexes, Cu(tbmp)nBr (n=1,2) and Cu(tbmpH)X2 (X=Cl-, Br-). Crystallographic studies are reported for Cu(tbmp)Br2, Cu(tbmp)2Br and Cu(tbmpH)Br2. Cu(tbmp)Br2 crystallizes as discrete, non-centrosymmetric dibromo-bridged dimers ([Ci(tbmp)Br2]2), in which each Cu(II) centre has a distorted tetragonal pyramidal environment. The tetrahedrally distorted basal plane of each Cu(II) centre consists of one thioether sulphur ligand, (mean Cu(II)-S = 2.352(6) Å), one pyridyl nitrogen (mean Cu(II)-N = 2.06(2) Å) and two bromide ions [one terminal (mean Cu(II)-Br = 2.372(3) Å) and one bridging (mean Cu(II)-Br = 2.415(3) Å)]. The apex of each tetragonal pyramid is formed by a long bond to the bridging, basal bromide ion (mean Cu(II)-Br = 2.902(4) Å) of the second Cu(II) centre. In monomeric, distorted tetrahedral Cu(tbmp)2Br, each Cu(I) ion is bound by a terminal bromine (Cu(I)-Br = 2.426(2) Å), two thicether sulphur atoms (mean Cu(I)-S = 2.331(4) Å) and a pyridyl nitrogen (Cu(I)-N = 2.11(1) Å). Cu(tbmpH)Br2 forms centrosymmetric dimers ([Cu(tbmpH)Br2]2), in which the distorted tetrahedral Cu(I) centres are bridged by two bromide ions (mean Cu(I)-Br = 2.597(1) Å). The two remaining coordinating positions of each Cu(I) ion are occupied by a terminal bromide ion (Cu(I)-Br = 2.363(1) Å) and a sulphur-bound (Cu(I)-S = 2.276 (2) Å) tbmpH+ cation. The structural data for these and related complexes are used in attempting to understand the nature of Cu(I) and Cu(II) interactions with biologically relevant ligands. The spectroscopic data suggests that the Cu(tbmp)2X2 complexes are cis-octahedral in the solid state, whereas the [Cu(tbmp)2X]BF4 complexes are tetragonal pyramidal. An unstable deep blue species is formed by the addition of t-butyl thiolate to Cu(tbmp)2X2, where X is Cl04- or BF4-. The displacement of tbmp (by pyridine) from Cu(tbmp)2X2 (X = Cl-, BF4-) is also discussed. With Co(II) and Ni(II), the cis-octahedral M(tbmp)2X2 (X=Cl-,Br-) and M(tbmp)2(Cl04)2.nH20 (n = 1,2) complexes have been characterized. The nature of paramagnetic metal ion [M=Cu(II), Co(II)] interactions with tbmp under hydrophobic conditions are investigated using 1H nmr spectroscopy. ii ) Complexes of 2-ethylthioethylamine (etea) The tetragonal complexes Cu(etea)X2 (X=Cl-, Br-), Cu(etea)2X2 (X=BF4-, ClO4-, Cl-, Br-) and [Cu(etea)2Cl]BF4 have been characterized and the displacement of etea from Cu(etea)2(Cl04)2 (by pyridine), is discussed. iii) Complexes of 2-methylthio-2-imidazoline (mti) In the reactions of mti with M(II), the tetragonal complexes Cu(mti)4X2 (X = BF4-, Cl-, Br-) were successfully synthesized, together with a tetrahedral complex, Co(mti)3Cl2. In the latter, one mti molecule appears to remain uncomplexed. With Cu(mti)4(BF4)2, the ligand is not displaced by an excess of pyridine. A 1H nmr line broadening experiment provides good evidence for Cu(II) binding to mti via its non-protonated nitrogen. iv) Complexes of 2-( 3, 3-dimethyl-2-thiabutyl)quinoline (tbmp) With this ligand, the pseudotetrahedral Cu(II) complexes, Cu(tbmp)X2 (X = Cl-, Br-) and the Cu(I) complexes, Cu(tbmq)Br, Cu( tbmqH)Br2 and Cu(tbmq)2Cl04, were synthesized. In contrast to tbmp and etea, tbmq does not form the six-coordinate complexes, Cu(tbmq)2X2 (X = Cl-, Br-). v) Complexes of 3-(2-methylthiophenylimino)camphor (L) Although L is susceptible to hydrolysis, the successful isolation and characterization of the pseudotetrahedral CuL(Cl04)2.acetone.xH20 (x = 0,2) complexes was achieved from acetone solutions. A 1H nmr line broadening experiment indicates that Cu(II)/S(thioether) interactions take place under hydrophobic conditions. vi) Complexes of 1,2-bis(pentafluorophenylthio)ethane (fpte) and ethylthiopentafluorobenzene (C6F5SEt) In order to determine the effects of the electronegative pentafluorophenyl substituents, the spectroscopic data for cis-PtCl2fpte, cis-PdCl2fpte and trans-PtCl2(C6F5SEt)2 are compared with the data for some related thioether ligand complexes. The results can be explained by a comparison of the ionisation potentials of the sulphur lone-pair electrons of fpte (as determined by photoelectron spectroscopy) with those of 3,4-bis(alkylthio)toluene (alkyl = methyl, ethyl) and meta- and para-bis (methylthio) benzene. SECTION II All of the carbonyl complexes in this Section have been characterized by infrared and electronic spectroscopy and in most cases, 1H nmr spectroscopy. i) Complexes of 3,4-bis(methylthio)toluene (bmtt) and 3,4-bis(ethylthio)toluene (bett) The bridged-ligand complexes, [M(CO)5]2bmtt and [M(CO)5]2bett (M=Cr, W), and the chelated-ligand complexes, M(CO)4bmtt and M(CO)4bett (M=Cr, Mo, W) were characterized in this study. On the basis of force constant calculations and electronic spectra, it is apparent that for aryl thioether ligands such as bmtt and bett, the sulphur atom acts as a poorer σ-donor and, in general, a better Π-acceptor than it does in aliphatic thioether ligands. A similar conclusion is reached for C6F5SEt (see above), with which unstable M(CO)5C6F5SEt (M=Cr, W) complexes were synthesized. Reactivity studies are reported for [W(CO)5]2bett and the mass spectra of [W(CO)5]2bmtt and the M(CO)4bmtt (M=Cr, Mo, W) complexes are discussed. 13C nmr spectra were recorded for [W(CO)5]2bmtt, M(CO)4bett (M=Cr, W), Cr(CO)4bmtt and the ligands. The 13CO chemical shifts for [W(CO)5]2bmtt and the W(CO)5L complexes of phosphorus and nitrogen ligands are correlated with their Cotton-Kraihanzel carbonyl force constants. ii) Complexes of 2-ethylthioethylamine (etea) and 2-( 3, 3-dimethyl-2-thiabutyl)pyridine (tbmp) Both the bridged-ligand [M(CO)5]2etea (M=Cr,W) and the chelated-ligand M(CO)4etea (M=Cr, Mo, W) complexes were characterized for etea. However, only the chelated-ligand complexes were isolated and characterized for tbmp. 13C nmr spectra for etea, Cr(CO)4etea and Mo(CO)4etea (the carbonyl complexes showing two distinct trans-13CO resonances) and reactivity studies for [W(CO)5]2etea and W(CO)4etea, are also discussed. iii) Complexes of 2-methylthioaniline (mta), 2-methylmercaptobenzimidazole (mmbi) and 2-methylthio-2-imidazoline (mti) The combined spectroscopic data for the M(CO)5L complexes of these ligands, shows that mmbi and mti prefer to bind to the zero-valent Group VIB metals via one of their nitrogen donors. On the other hand, mta prefers to bind via the thioether sulphur. Although the complexes of mta could not be isolated in an analytically pure form, good evidence for their identities was provided by their infrared and mass spectra and the observed replacement of mta from W(CO)5mta, by triphenylphosphite.Item DFT calculations on the interaction of phosphazenes with transition metals : a thesis presented in partial fulfillment of the requirements for the degree of Master of Science in Chemistry at Massey University, Palmerston North(Massey University, 2007) Davidson, Ross JamesThe electronic structure of substituted cyclic phosphazenes has been investigated using Density Functional Theory (DFT) and Natural Bond Order (NBO) analysis. NBO analysis shows covalent, ionic and negative hyper-conjugation interactions all contribute to the electronic structure of cyclic phosphazenes. The geometric and electronic structural changes that occur when transition metals are coordinated to the nitrogen atom of the phosphazene ring have been analyzed using the NBO model. The bonding of transition metal ions with the ring nitrogen on the phosphazene was investigated by modeling hexakis(2-pyridyloxy)cyclotriphosphazene, hexakis(4-methyl-2-pyridyloxy)cyclotriphosphazene and octakis(2- pyridyloxy)cyclotetraphosphazene with different metal ions (Co(II), Ni(II), Cu(II), Zn(II)) in their assorted configurations with DFT as implemented in the Gaussian03 package. First-row transition metals bind to the phosphazene ring with simple s donor behaviour via the ring nitrogen. The lengthening of the PN bonds adjacent to the coordinated metal centre is a result of electron density being removed from the PN bonding orbitals and going into the 4s orbital of the metal ion. Investigating the pyridine substituents on the phosphazene ring showed that these can affect the PN bonds in a similar fashion, although weaker, to the transition metals. This effect is the result of the pyridine nitrogen lone pair affecting the negative hyperconjugation component of the PN bond. Coupling between two metal atoms coordinated to the phosphazene ring was investigated by DFT calculations, which showed molecular orbitals in both the tricyclic and tetracyclic phosphazene capable of providing an ‘electron density bridge’ between the metal centres. These results are in accord with ESR and magnetic susceptibility results, which can be explained in terms of weak antiferromagnetic coupling between metal ions. The cyclic phosphazenes are model compounds for polyphosphazenes and the results obtained from this work will provide insight into the electronic properties of this important class of inorganic polymers.Item Cyclo- and polyphosphazenes containing 2-oxypyridine moieties coordinated to selected transition metals : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Chemistry at Massey University, Palmerston North(Massey University, 2008) Kirk, StephenThe phosphazene ligands spiro(biph)tetrakis(2-oxypyridine)cyclotriphosphazene (L1), spiro(biph)tetrakis(4-methyl-2-oxypyridine)cyclotriphosphazene (L2), and spiro(biph)tetrakis(6-methyl-2-oxypyridine)cyclotriphosphazene (L3 In solution, [CuL) have been synthesised and characterised as small molecule templates for the polymeric analogues. Complexes of each ligand with selected transition metals have been synthesised and characterised. Where X-ray crystal structures have been obtained, the predominant geometry is a five-coordinate trigonal bipyramidal (TBP) form, though variations exist. 2Cl2] retains the TBP form whereas [CoL2Cl2 ] rearranges to a tetrahedral geometry. In order to elucidate this behaviour, diamagnetic complexes were synthesised and variable temperature NMR (VTNMR) studies conducted. The complexes [ZnL2Cl2], [CdL2Cl2] and [HgL2Cl2] exhibit fluxional behaviour as monitored by VTNMR studies. The X-ray structure of [CdL2Cl2] contains three molecules in the unit cell that demonstrate what is thought to be the first evidence for a fluxional mechanism in phosphazene compounds. The complex [ZnL2Cl2 ] exists at low temperature as discernable major and minor species. Polyphosphazene analogues have been synthesised and complexed with selected transition metals. The polymer complexes display variations in solubility and stability which is postulated to be due to the ratio of side group substitution, position of the pyridyl methyl group and the nature of the complexing metal. A number of the polymers degrade prior to workup, possibly as a result of base-promoted attack on the backbone by the pyridyl nitrogen atoms. Electronic spectra reveal that where soluble, the Co(II) polymer complexes have a tetrahedral geometry, whereas the Cu(II) polymer complexes distort between TBP and square-based pyramidal dependent on the ratio of metal used. Polymer complexes with Zn(II) demonstrate fluxional behaviour.