113 results for Henderson, William, Journal article

  • Study of metal scrambling in the trinuclear {Pt₂Se₂M} (M = Pt, Pd, Au) system using an electrospray mass spectrometry (ESMS) directed synthetic methodology; isolation and crystallographic characterization of {Pt₂(µ₃-Se)₂(PPh₃)₄[Pt(cod)]}{PF₆}₂ and {Pt(μ₃-Se)₂(PPh₃)₂[Pt(cod)]₂}{PF₆}₂ (cod = Cyclo-octa-1,5-diene)

    Yeo, Jeremy S.L.; Vittal, Jagadese J.; Henderson, William; Hor, T.S. Andy (2002)

    Journal article
    University of Waikato

    Pt₂(μ-Se)₂(PPh₃)₄ reacts with PtCl₂(cod) to give {Pt₂(μ₃-Se)₂(PPh₃)₄[Pt(cod)]}²⁺ and an unexpected cod-rich product that arises from metal scrambling, viz. {Pt(μ₃-Se)₂(PPh₃)₂[Pt(cod)]₂}²⁺. The formation of these species was detected and followed by electrospray mass spectrometry (ESMS) and subsequently verified by batch synthesis and crystallographic characterization. Other metal-scrambled aggregate products were successfully detected.

    View record details
  • Use of cyclometallated PdCl[PPh₂CH₂CH₂CHCH₂CH₂PPh₂] as a precursor to homo and heterometallic species directed by ESMS (Electrospray Ionisation Mass Spectrometry)

    Neo, Kian Eang; Neo, Yew Chin; Chien, Sheau Wei; Tan, Geok Kheng; Wilkins, Alistair L.; Henderson, William (2004)

    Journal article
    University of Waikato

    The cyclometallated Pd compound PdCl[PPh₂CH₂CH₂CHCH₂CH₂PPh₂] 1, obtained from PdCl₂(Ph₂P(CH₂)₅PPh₂) in refluxing DMF (N,N-dimethylformamide), was characterized by NMR and X-ray single-crystal diffraction analysis. The cyclometallation of MCl₂(Ph₂P(CH₂)₅PPh₂)(M = Pd, Pt) to give 1 and its Pt(II) analogue was probed using electrospray ionisation mass spectrometry (ESMS). The reactivity of 1 towards neutral ligands such as phosphines and pyridines as well as basic metal complexes such as pyridine-thiolate compounds of Au(I), Hg(II) and Pt(II) in solution was also investigated. The results showed that the chloride trans to the Pd–C bond is susceptible to ligand replacement. A number of entry metalloligands was examined in an attempt to establish a route to cyclometallated aggregates and clusters.

    View record details
  • Self-assembly of a columnar polymeric calcium phosphinate derived from camphene

    Henderson, William; Leach, Meto T.; Nicholson, Brian K.; Sabat, Michal (1995)

    Journal article
    University of Waikato

    (2,2-Dimethylbicyclo[2.2.1] hept-3-ylmethyl)phosphinic acid (RPO₂H₂), readily prepared from camphene and hypophosphorous acid, formed a polymeric calcium salt [{Ca(RPO₂H) ₂ (RPO₂H₂)(H₂O)}n], with both terminal and triply bridging phosphinate groups, and an overall columnar structure with an inorganic core and a pseudo-close-packed sheath of terpene moieties.

    View record details
  • E/Z isomerism in monoalkylated derivatives of [Pt₂(μ-S)₂(PPh₃)₄] containing 2,4-dinitrophenylhydrazone substituents

    Ujam, Oguejiofo Theophilus; Devoy, Sarah M.; Henderson, William; Wilkins, Alistair L.; Nicholson, Brian K. (2011)

    Journal article
    University of Waikato

    Alkylation of [Pt₂(m-S)₂(PPh₃)₄] with 2,4-dinitrophenylhydrazone-functionalized alkylating agents XC6H4C{¼NNHC₆H₃(NO₂)₂}CH2Br (X¼H, Ph) gives monoalkylated cations [Pt₂(m-S){m-SCH₂C{¼NNHC₆H₃(NO₂)₂}C₆H₄X}(PPh₃)₄]⁺. An X-ray diffraction study on [Pt₂(m-S){m-SCH₂C{¼NNHC₆H₃(NO₂)₂}Ph}(PPh₃)₄]BPh₄ shows the crystal to be the Z isomer, with the phenyl ring and NHC₆H₃(NO₂)₂ groups mutually trans. ¹H- and ³¹P{¹H} NMR spectroscopic methods indicate a mixture of Z (major) and E (minor) isomers in solution, which slowly convert mainly to the E isomer. Reaction of [Pt₂(m-S)₂ (PPh₃)₄] with the dinitrophenylhydrazone of chloroacetone [ClCH₂C{¼NNH(C₆H₃(NO₂)₂}Me] and NaBPh₄ gives [Pt₂ (m-S){m-SCH₂C{¼NNHC₆H₃(NO₂)₂}Me}(PPh₃)₄]BPh₄, which exists as a single (E) isomer.

    View record details
  • Sonochemical preparation of single-dispersion metal nanoparticles from metal salts

    Fujimoto, Toshiyuki; Terauchi, Shin-ya; Umehara, Hiroyuki; Kojima, Isao; Henderson, William (2001)

    Journal article
    University of Waikato

    Novel metal nanoparticles of Pd and Pt were prepared by sonochemical reduction of solutions containing H₂PtCl₆ or K₂PdCl₄. The effect of atmospheric gas on the particle size distribution was investigated. Average diameters and standard deviations of the Pd particles prepared under Ar (Pd/Ar) and N2 (Pd/N₂) were found to be 3.6 ± 0.7 nm (Pd/Ar) and 2.0 ± 0.3 nm (Pd/N₂). Smaller and sharper distribution of the particle size was observed for the Pd particles formed under a N₂ atmosphere. In the case of Pt, a smaller and sharper distribution of the particle size was observed for the particles prepared under a Xe atmosphere. These relations can be explained in terms of a hot-spot temperature created by acoustic cavitation.

    View record details
  • A zwitterionic monoalkylated derivative of [Pt₂(μ-S)₂(PPh₃)₄] from 1,3-propanesultone

    Ujam, Oguejiofo Theophilus; Henderson, William; Nicholson, Brian K. (2013)

    Journal article
    University of Waikato

    Reaction of dinuclear platinum(II) sulfido complex [Pt₂(μ-S)₂(PPh₃)₄] with 1,3-propanesultone gives the novel zwitterionic monoalkylated thiolate complex [Pt₂(μ-S){μ-S(CH₂)₃SO₃}•(PPh₃)₄], which was characterized by NMR spectroscopy, electrospray ionisation mass spectrometry, and a single crystal X-ray structure determination. Crystals are monoclinic, space group P2(1)/c with unit cell dimensions a = 16.8957(3) Å, b = 15.5031(3) Å, c = 28.0121(5) Å, β = 99.780(1)°, for Z = 4.

    View record details
  • The chemistry and metallurgy of beryllium

    Raymond, Onyekachi; Perera, Lakshika C.; Brothers,, Penelope J.; Henderson, William; Pleiger, Paul G. (2015-07)

    Journal article
    University of Waikato

    Beryllium (Be), the first of the group 2 alkali-earth ele­ments, is a silver-gray metal possessing an unmatched combination of physical and mechanical properties, which are vital for a variety of applications that offer tre­mendous benefits to society. It is the lightest workable metal, only two-thirds the weight of aluminium, yet it has six times the stiffness of steel, making it an ideal mate­rial for stiffness-dependent and weight-limited applica­tions. The chart in Fig. 1 illustrates how much beryllium outclasses other engineering materials with respect to thermal conductivity and dimensional stability (ability of a material to retain its uniformity under stress measured as the Young's modulus to density ratio). These unique properties of beryllium translate into performance en­hancement in the end product, for instance the James Webb Space Telescope (JWST: see Fig. 2). The next gen­eration James Webb Space Telescope, scheduled to be launched in 2018 as NASA's replacement for the Hubble telescope, will utilise a 6.5 meter wide beryllium mirror to reveal images of distant galaxies 200 times beyond what has ever been sighted.

    View record details
  • Properties of a thermostable β-glucosidase immobilized using tris(hydroxymethyl)phosphine as a highly effective coupling agent

    Oswald, Paul R.; Evans, Rachel A.; Henderson, William; Daniel, Roy M.; Fee, Conan J. (1998)

    Journal article
    University of Waikato

    A very stable b-glucosidase (EC 3.2.1.21) was immobilized to polyacrylamide-magnetite beads, aminopropyl silica, and chitosan using tris(hydroxymethyl)phosphine (THP) or glutaraldehyde as the coupling reagent. The use of THP on chitosan resulted in greater than 90% yields with respect to free enzyme activity compared with only 60% observed when using the more conventional glutaraldehyde coupling reagent. THP-immobilized enzyme also lost activity more slowly than both glutaraldehyde-immobilized and the free enzyme when incubated at 90°C. Repetitive assays of THP and glutaraldehyde-immobilized enzyme also showed that THP was more able to retain active enzyme on the silica-based support. The pH optimum and Km app were unchanged with respect to free enzyme.

    View record details
  • Hydrogen bonding in hydroxymethylphosphine chalcogenides

    Goodwin, Nicholas J.; Henderson, William; Nicholson, Brian K. (2002-06-01)

    Journal article
    University of Waikato

    Hydrogen bonding in the phosphine chalcogenide series Ph2P(X)CH2OH (X=O, 1; S, 2; Se, 3) has been investigated by single crystal X-ray crystallography. While the phosphine oxide exhibits a dimer motif, the sulfide and selenide form infinite chains; in all cases hydrogen bonding is from the OH group to the phosphine chalcogenide heteroatom. The trend in the hydrogen bond angle for OH X-P, which is 117, 87 and 84° for the oxide, sulfide and selenide, respectively, is explained with respect to the geometry of electron density on the phosphine chalcogenide heteroatom.

    View record details
  • Synthesis and structural characterisation of the lead–platinum sulfido aggregates [Pt₂(μ-S)₂(PPh₃)₄PbX₂] (X = Br, I); promotion of rare tetrahedral geometry for lead(II)

    Henderson, William; Hor, T.S. Andy (2010-05-05)

    Journal article
    University of Waikato

    The reactions of [Pt₂(μ-S)₂(PPh₃)₄] with excess PbBr₂ or PbI₂ in methanolic suspension result in the formation of the neutral lead(II) halide adducts [Pt₂(μ-S)₂(PPh₃)₄PbX₂] (X = Br, I). The X-ray structure determination of the lead iodide adduct reveals an essentially tetrahedral lead(II) centre, which is a rare coordination geometry for lead(II), which almost invariably is hemidirected, with a stereochemically active lone pair. In contrast, the structure of the PbBr2 adduct, although suffering from some disorder, shows a more typical, distorted arrangement of ligands; these results are discussed in terms of the tendency for soft, bulky ligands to promote symmetric, holodirected geometries. The ESI mass spectra of the adducts are reported, and yield [M−halide]⁺ ions.

    View record details
  • (p -Cymene)thioglycollatoruthenium(II) dimer; a complex with an ambi-basic S,O-donor ligand

    Henderson, William; Kilpin, Tracey D.; Nicholson, Brian K. (2007)

    Journal article
    University of Waikato

    The title compound was prepared from the (p-cymene)ruthenium chloride dimer and thioglycollic acid. The structure is a centrosymmetric dimer bridged by the soft-base S atoms, with the hard-base O atoms of the carboxylate group chelating to form a five-membered twisted-ring. The coordination of the ruthenium atoms is completed by a η6-p-cymene ligand, giving an 18-electron count. The Ru–S bonds are essentially equal at 2.396(1) Å.

    View record details
  • Coordination polymers and isomerism; a study using silver(I) and a ∏-stacked ligand

    Caradoc-Davies, Paula L.; Hanton, Lyall R.; Henderson, William (2001)

    Journal article
    University of Waikato

    The ligand 2,5-bis(2-pyridylmethylsulfanylmethyl)pyrazine (L) was prepared by the base coupling of 2-(sulfanylmethyl)pyridine and 2,5-bis(chloromethyl)pyrazine. This new ligand was treated with AgClO₄ in a 1 1 metal-to-ligand ratio and with AgNO₃in a 2 1 metal-to-ligand ratio to give coordination polymers. The crystal structures of {[Ag(L)]ClO₄}∞ ( 1) and {[Ag₂(L)](NO₃)₂}∞ ( 2) were determined. The Ag(I) ions in the one-dimensional polymeric chains of 1 adopted square-pyramidal geometries with the pyridine and pyrazine N donors coordinated in an extremely bent fashion. The structure of 2 revealed two isomeric polymer chains in the one crystal forming a single supramolecular array. The isomeric polymers differed in the donor atoms about the Ag(I) ions and in the arrangement of adjacent ligands along the chain. A feature of both structures was that L adopted a three-layer ∏-stacked arrangement.

    View record details
  • Characterization of synthetic and commercial trisiloxane surfactant materials

    Bonnington, L. S.; Henderson, William; Zabkiewicz, J. A. (2004)

    Journal article
    University of Waikato

    The organosilicone surfactant Silwet L-77® (L-77), used as an agrochemical adjuvant, is a mixture comprised predominantly of [(CH₃)₃SiO]₂ (CH₃)Si (CH₂)₃ (OCH₂CH₂)n OCH₃ oligomers (n = 3-16, average n 7.5). The commercially available L-77 mixture was purified by reversed-phase high-performance liquid chromatography (HPLC) to obtain individual trisiloxane surfactant components. Pure oligomers (n = 3, 6 and 9) were also synthesized. Synthesis was achieved by hydrosilylation of monomeric ethoxylate monomethyl ether starting reagents. Pure hexa- and nona-ethylene glycols were produced by condensation of smaller oligomers. Atmospheric-pressure ionization mass spectrometry (MS) methods were used to characterize fully the commercial L-77 product and synthesized or isolated components. The application of Fourier-transform ion cyclotron resonance MS and online HPLC-electrospray ionization MS techniques to the analysis of this surfactant are described here. The application of these analytical techniques also enabled elucidation of the synthetic by-products present in the commercial formulation.

    View record details
  • Electrospray ionisation - a simple prelude to the understanding of other mass spectrometry techniques

    Henderson, William (2015-07)

    Journal article
    University of Waikato

    Mass spectrometry (MS) is a powerful analytical technique used in the characterisation of a wide range of chemical and biochemical substances. The technique is extensively used in research, across a wide range of disciplines. One of the main strengths of mass spectrometry is that miniscule amounts of sample are typically needed, in the order of micrograms or less. While the study of spectroscopic techniques has been a part of qualifications such as the International Baccalaureate Diploma for some time, ¹ a new Achievement Standard on Spectroscopy has been introduced relatively recently into the New Zealand Chemistry Curriculum, which includes the technique of electron ionisation (El) mass spectrometry.² This article aims to provide, for those perhaps encountering mass spectrometry for the very first time, a short discussion on electrospray ionisation mass spectrometry as an alternative introduction to this important analytical technique.

    View record details
  • Bis[μ-bis(diphenylphosphino)methane-К²P:P’]bis[(saccharinato-КN)- palladium(I)] dichloromethane solvate

    Henderson, William; Nicholson, Brian K.; Chung, Dong C. (2002)

    Journal article
    University of Waikato

    The dimeric palladium(I) saccharinate complex [Pd₂(sac)₂(dppm)₂], has been characterized as its di¬chloro¬methane solvate, i.e. [Pd₂(C₇H₄NO₃S)₂(C₂₅H₂₂P₂)₂]•CH₂Cl₂. The complex features a Pd—Pd bond bridged by two dppm ligands, with the saccharinate ligands N-bonded trans to the Pd—Pd bond.

    View record details
  • Fragmentation pathways of [Re₂(μ-OR)₃(CO)₆]– (R = H, Me) and ligand exchange reactions with oxygen donor ligands, investigated by electrospray mass spectrometry

    Jiang, Chenghua; Hor, T.S. Andy; Yan, Yaw Kai; Henderson, William; McCaffrey, Louise J. (2000)

    Journal article
    University of Waikato

    The rhenium hydroxy and methoxy carbonyl complexes [Re₂(μOR)₃(CO)₆]⁻ (R = H or Me) have been studied by negative-ion electrospray mass spectrometry (ESMS). The complexes undergo facile exchange reactions with protic compounds, including alcohols and phenols. With dimethyl malonate, ester hydrolysis occurs giving carboxylate-containing complexes, and with H₂O₂ or ButOOH, oxidation to ReO₄⁻occurs. The feasibility and extent of these reactions can conveniently, rapidly, and unambiguously be determined by electrospray mass spectrometry, and is dependent on the acidity and steric bulk of the protic compound. The results also suggest that the complexes can be used as versatile starting materials for the synthesis of a wide range of analogous [Re₂(μ-OR)₃(CO)₆]⁻ complexes by simple reaction with an excess of the appropriate alcohol. By varying the applied cone voltage the fragmentation pathways have been investigated; the hydroxy complex undergoes dehydration followed by CO loss, whereas for the methoxy complex -hydride elimination (and CO loss) is observed, with confirmation provided by deuterium labelling studies. Under ESMS conditions, the neutral complexes [Re₂(μ-OR)₂(μ-dppf )(CO)₆] [R = H or Me; dppf = 1,1 -bis(diphenylphosphino)ferrocene] undergo substantial solvolysis and hydrolysis to give mainly mononuclear species; simple parent ions (e.g. [M + H]⁺) are not formed in appreciable abundance, probably due to the lack of an efficient ionisation pathway.

    View record details
  • Ligand exchange reactions of [Re₂(μ-OR)₃(CO)₆]⁻(R = H, Me) with sulfur, selenium, phosphorus and nitrogen donor ligands, investigated by electrospray mass spectrometry

    Jiang, Chenghua; Hor, T.S. Andy; Yan, Yaw Kai; Henderson, William; McCaffrey, Louise J. (2000)

    Journal article
    University of Waikato

    Negative-ion electrospray mass spectrometry has been used to investigate the reactions of the dinuclear rhenium aggregates [Re₂(μ-OH)₃(CO)₆]⁻ 1 and [Re₂(μ-OMe)₃(CO)₆]⁻ 2 with a range of thiols, benzeneselenol, and some other sulfur-, phosphorus- and nitrogen-based ligands. Typically up to three of the hydroxo ligands are replaced by simple thiolates, giving the series of species [Re₂(OH)₂(SR)(CO)₆]⁻, [Re₂(OH)(SR)₂(CO)₆]⁻, and [Re₂(SR)₃(CO)₆]⁻. Similarly, reaction of 1 with H₂S gives the species [Re₂(μ-SH)₃(CO)₆]⁻, which undergoes an analogous fragmentation process to [Re₂(μ-OH)₃(CO)₆]⁻, at high cone voltages, by loss of H₂S and formation of [Re₂(S)(SH)(CO)₆]⁻. With ligands which are good chelating agents (such as dithiocarbamates R₂NCS₂⁻, and thiosalicylic acid, HSC₆H₄CO₂H) initial substitution of one or two OH groups readily occurs, but on standing the dimer is cleaved giving [Re(S₂CNR₂)₂(CO)₃]⁻ and [Re(SC₆H₄CO₂)(CO)₃]⁻. The different reactivities of the dithiol reagents benzene-1,2- and benzene-1,4-dimethanethiol towards 1 are also described. Complex 1 also reacts with aniline, and with primary (but not secondary) amides RC(O)NH₂, giving monosubstituted species [Re₂(OH)₂(NHPh)(CO)₆]⁻ and [Re₂(OH)₂{NHC(O)R}(CO)₆]⁻ respectively. The reactions with adenine and thymine, and with the inorganic anions thiocyanate and thiosulfate, are also described.

    View record details
  • Ferrocenyl hydroxymethylphosphines (η⁵-C₅H₅)Fe[η⁵⁻C₅H₄P(CH₂OH)₂] and 1,1′-[Fe{η⁵-C₅H₄P(CH₂OH)₂}₂] and their chalcogenide derivatives

    Henderson, William; Alley, Steven R. (2002)

    Journal article
    University of Waikato

    The ferrocenyl hydroxymethylphosphines FcP(CH₂OH)₂ [Fc=(η⁵-C₅H₅)Fe(η⁵-C₅H₄)] and 1,1′-Fc′[P(CH₂OH)₂]₂ [Fc′=Fe(η⁵⁻C₅H₄)₂] were prepared by reactions of the corresponding primary phosphines FcPH₂ and 1,1′-Fc′(PH₂)₂ with excess aqueous formaldehyde. The crystal structure of FcP(CH₂OH)₂ was determined and compared with the known ferrocenyl hydroxymethylphosphine FcCH₂P(CH₂OH)₂. The chalcogenide derivatives FcP(E)(CH₂OH)₂ and 1,1′-Fc′[P(E)(CH₂OH)₂]₂ (E=O, S, Se) were prepared and fully characterised. Crystal structure determinations on FcP(O)(CH₂OH)₂ and FcP(S)(CH₂OH)₂ were performed, and the hydrogen-bonding patterns are compared with related compounds. The sulfide shows no hydrogen-bonding involving the phosphine sulfide group, in contrast to other reported ferrocenyl hydroxymethylphosphine sulfides. The platinum complex cis-[PtCl₂{FcP(CH₂OH)₂}₂] was prepared by reaction of 2 mol equivalents of FcP(CH₂OH)₂ with [PtCl₂(1,5-cyclo-octadiene)], and was characterised by 31P-NMR spectroscopy and negative ion electrospray mass spectrometry, which gave a strong [M+Cl]⁻ ion.

    View record details
  • New ferrocene-derived hydroxymethylphosphines: FcP(CH₂OH)₂ [Fc=(η⁵-C₅H₅)Fe(η⁵-C₅H₄)] and the dppf analogue 1,1′-Fc′[P(CH₂OH)₂]₂ [Fc′=Fe(η⁵-C₅H₄)₂]

    Alley, Steven R.; Henderson, William (2001)

    Journal article
    University of Waikato

    Reactions of the ferrocene-phosphines FcPH₂ and 1,1′-Fc′(PH₂)₂ with excess formaldehyde gives the new hydroxymethylphosphines FcP(CH₂OH)₂ 1 and 1,1′-Fc′[P(CH₂OH)₂]₂ 2, respectively. Phosphine 1 is an air-stable crystalline solid, whereas 2 is isolated as an oil. Reaction of 1 with H₂O₂, S₈ or Se gives the chalcogenide derivatives FcP(E)(CH₂OH)₂ (E=O, S or Se), whilst reaction of 2 with S8 gives 1,1′-Fc′[P(S)(CH₂OH)₂]₂, which were fully characterised. Phosphine 1 was also characterised by an X-ray crystal structure determination.

    View record details
  • Synthesis and structure of the amidate-bridged platinum-uranium bimetallic complex [Pt{NC(O)CH₂CH₂}₂(PPh₃)₂].UO₂(NO₃)₂

    Henderson, William; Oliver, Allen G.; Rickard, Clifton E.F. (2000)

    Journal article
    University of Waikato

    The reaction of the β-propiolactam-derived platinum(II) amidate complex [Pt{NC(O)CH₂CH₂}₂(PPh₃)₂]with uranyl nitrate gives the coordination complex [Pt{NC(O)CH₂CH₂}₂(PPh₃)₂].UO₂(NO₃)₂, which was characterised by a single-crystal X-ray diffraction study. The lactam carbonyl groups are coordinated to the linear uranyl group, forming an eight-membered ring, with the uranium also having two bidentate nitrates, completing a hexagonal bipyramidal coordination geometry. The platinum and uranium coordination planes are almost perpendicular, at an angle of 85.4(1)°.

    View record details