143 results for Nicholson, Brian K., ResearchCommons@Waikato

  • New ruthenium carbonyl clusters containing unusual 5-sulfido-, 4-benzyne-, and thianthrene-derived ligands: Insertion of ruthenium into the thianthrene ring by C-S activation

    Hassan, Mohammad R.; Kabir, Shariff E.; Nicholson, Brian K.; Nordlander, Ebbe; Uddin, Md. Nazim (2007-07-01)

    Journal article
    University of Waikato

    Treatment of [Ru3(CO)12] with thianthrene in refluxing toluene afforded [( 4-S)Ru4( -CO)2(CO)9( 4- 2-C6H4)] (1), [( 5-S)Ru6( -CO)2(CO)15( - 3-C12H8S)] (2), and [( 5-S)Ru5( -CO)2(CO)11( - 3-C12H8S)( 4- 2-C6H4)] (3) in 18%, 8%, and 16% yields, respectively. Thermolysis of 2 in refluxing heptane gave compounds 1 and 3. A similar thermolysis of 3 in refluxing toluene gave 1 in 90% yield. Treatment of 3 with neat MeCN afforded the labile compound [( 5-S)Ru5( -CO)2(CO)10( - 3-C12H8S)( 4- 2-C6H4)(MeCN)] (4) in 73% yield. The reaction of 4 with P(OMe)3 gave the substitution product [( 5-S)Ru5( -CO)2(CO)10( - 3-C12H8S)( 4- 2-C6H4){P(OMe)3}] (5) in 52% yield. Compounds 1-4 have been structurally characterized. Compound 1 contains a 4-capping sulfido and a 4- 2-benzyne ligand, whereas 3, 4, and 5 contain 5-sulfido and 4- 2-benzyne ligands. The latter three compounds provide rare examples of 5-sulfido and metal-assisted opening of the thianthrene ligand on polynuclear centers. In compounds 1, 3, and 4 the 4- 2-benzyne ligand is perpendicular to the Ru4 face of the clusters and represents a previously uncharacterized bonding mode for benzyne.

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  • β-Cyclomanganated 1,5-diphenylpenta-1,4-dien-3-ones and their reactions with alkynes: routes to η5-pyranyl--- and η5-oxocycloheptadienyl---Mn(CO)3 complexes

    Tully, Warren; Main, Lyndsay; Nicholson, Brian K. (2001-08-01)

    Journal article
    University of Waikato

    1,5-Diphenylpenta-1,4-dien-3-ones (4) are cyclometalated with benzylpentacarbonylmanganese to form [[1-phenyl-2-((E)-3-phenylprop-2-en-1-oyl-κO)]ethenyl-κC1]tetracarbonylmanganese derivatives (5). Coupling of 5 with alkynes in some cases gives [4-phenyl-2-(2-phenylethenyl)pyranyl-η5]tricarbonylmanganese complexes (6) analogous to those previously reported for β-manganated chalcones, but in other cases an alternative cyclisation pathway subsequent to insertion of alkyne into the C---Mn bond leads to [6-oxo-4,7-diphenylcyclohepta-1,4-dienyl-1,2,3,4,5-η]tricarbonylmanganese complexes (7). The X-ray crystal structure determination is reported for one such compound, [6-oxo-2,4,7-triphenylcyclohepta-1,4-dienyl-1,2,3,4,5-η]tricarbonylmanganese (7a), derived from 1,5-diphenylpenta-1,4-dien-3-one and phenylacetylene. The 7-phenyl group is found to occupy the endo position, and a mechanism involving Mn-mediated aryl migration is suggested to explain this stereochemistry. The reaction of 7a with ammonium cerium(IV) nitrate gives a low yield of 2-nitro-3,5,7-triphenylcyclohepta-2,4,6-trien-1-one (9), whose structure was established by X-ray crystal structure analysis. The pyranyl complexes (6) provide the corresponding pyrylium triiodide salts (8) when demetalated with iodine.

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  • 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.

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  • Cluster Chemistry : XVII.Radical ion-initiated synthesis of ruthenium cluster carbonyls containing tertiary phosphines, phosphites, arsines, SbPh₃, or isocyanides

    Bruce, Michael I.; Matisons, Janis G.; Nicholson, Brian K. (1983)

    Journal article
    University of Waikato

    The syntheses of over sixty known and new derivatives of Ru₃(CO)₁₂ and H₄Ru₄(CO)₁₂ by substitution reactions initiated by sodium diphenylketyl are described. The range of ligands studied includes isocyanides, tertiary phosphines and phosphites, tertiary arsines and SbPh₃. The reactions are characterised by high degrees of specificity and conversion: under mild conditions up to four ligands can be introduced. Comparisons with the corresponding thermally induced reactions are made in several cases. The reactions provide routes to mixed ligand derivatives of the cluster carbonyls, although account of relative Lewis base strengths of the ligands may have to be taken. Possible mechanisms of these reactions are discussed briefly, as are the IR ν (CO) spectra of the Ru₃ (CO)12-nLn complexes.

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  • Preparation and the crystal and molecular structure of [Net₄][Ge{Co₂(CO)₇}{Co₂(CO)₆[HgCo(CO)₄]}]: an anion containing a mercury-bridged cobalt–cobalt bond

    Duffy, D. Neil; Mackay, Kenneth M.; Nicholson, Brian K.; Robinson, Ward T. (1981)

    Journal article
    University of Waikato

    The title compound has been isolated from the reaction of Gel4 with Na[Co(CO)₄] in the presence of Hg and has been characterised by X-ray analysis. Crystals are triclinic, a= 12.065(1), b= 17.334(2), c= 9.222(1)Å, α= 95.17(3), β= 82.72(3), γ= 96.95(3)°, space group P , and Z= 2. The structure has been solved by direct methods and refined to R= 0.049 for 3 136 reflections [I 5σ(I)]. The anion contains a common Ge atom bridging the Co–Co bonds both of a Co₂(CO)₇ unit and of a Co₂(CO)₆ unit which is also bridged by a HgCo(CO)₄ group.

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  • Transition metal carbonyl derivatives of the germanes: XIV. Studies of mixed cobalt carbonyl/manganese carbonyl substituted germanes including [(CO)₅MnGeCo₃(CO)₉], μ₃-(pentacarbonylmanganesegermylidyne)cyclotris(tricarbonylcobalt)(3Co---Co)

    Christie, Judy A.; Duffy, D. Neil; Mackay, Kenneth M.; Nicholson, Brian K. (1982)

    Journal article
    University of Waikato

    [Mn(CO)₅GeH₃] reacts smoothly with Co₂(CO)₈ to form the [(CO)₅MnGeCo₃(CO)₉], which is also produced by the reaction of Mn(CO)₅⁻ with [(CO)₄CoGeCo₃(CO)₉]. [Mn(CO)₅GeMeH₂] similarly reacts with Co₂(CO)₈ to give [{Mn(CO)₅} {Co₂(CO)₇}GeMe]. The products were characterised spectroscopically and the ESR spectrum of the radical ion of the title compound is presented.

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  • Anionic germanium polycobalt carbonyl clusters. Part 3. Preparation and structures of [Net₄][Ge₂Co₇(CO)₂₁] and [Net₄][Ge{Co₇(CO)₂₀}]; two large clusters incorporating tetrahedral GeCo₃ units

    Duffy, D. Neil; Mackay, Kenneth M.; Nicholson, Brian K.; Thomson, Ralph A. (1982)

    Journal article
    University of Waikato

    Reactions of the [Ge{Co₅(CO)₁₆}]⁻ cluster have given rise to two new germanium–polycobalt cluster anions, characterised as their Net₄⁺ salts by X-ray crystallography. The complex [NEt₄][Ge₂Co₇(CO)₂₁](1a) forms triclinic crystals, space group P , with a= 13.085(2), b= 19.712(7). c= 12.220(8)Å, α= 109.10(3), β= 92.60(2), γ= 129.32(3)°, and Z= 2. The structure was solved by direct methods and refined to R=R′= 0.046 for 2 076 reflections with l > 3σ(l). The anion (1) consists of two –GeCo₃(CO)₉ units bonded mutually trans about a trigonal planar Co(CO)₃ group, giving idealised C3v, symmetry. For [Net₄][Ge{Co₇(CO)₂₀}](2a). crystals are monoclinic, space group P21/c, with a= l2.761(7), b= 18.415(3), c= 17.675(4)Å, β= 102.91(3)°, and Z= 4. The structure was refined to R= 0.077, R′= 0.074, for 1 123 reflections with I > 2σ(I). The anion (2) is a derivative of the C3v structure of [Co₄(CO)₁₂] with the axial carbonyl ligand of one basal cobalt replaced by a –GeCo₃-(CO)₉⁻ fragment. The Co4 tetrahedron is disordered.

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  • Anionic germanium polycobalt carbonyl clusters. Part 2. Preparation and structure of [Net₄][Ge{Co₅(CO)₁₆}], a cluster which contains five-co-ordinate germanium

    Croft, Rex A.; Duffy, D. Neil; Nicholson, Brian K. (1982)

    Journal article
    University of Waikato

    Addition of [Co(CO)₄]⁻ to [Ge{Co₄(CO)n}](n= 16, 14, or 13) under mild conditions gives good yields of [Ge{Co₅(CO)₁₆}]⁻. This forms crystals with Net₄⁺ which are orthorhombic, space group Pn2₁ a with a= 12.014(1), b= 36.938(4), c= 15.249(2), and Z= 8. The crystal structure was solved by direct methods and refined, with some difficulty due to pseudo-symmetry, to R= 0.088, R′= 0.081, for 1 590 unique reflections with F² > 2σ(F²). The anion has a GeCo₅ metal skeleton consisting of a GeCo₂ triangle and a GeCo₃ tetrahedron sharing a common apex at Ge. The five Ge–Co bond lengths vary from 2.33 to 2.51 Å. Three of the CO ligands on the GeCo₃ unit bridge the three Co–Co bonds, with two terminal CO groups on each Co atom. On the GeCo₂ moiety there are six terminal and one bridging carbonyls.

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  • Transition-metal carbonyl derivatives of the germanes. Part 13. Preparation, spectroscopic properties, and the crystal and molecular structure of bis[µ-carbonyl-bis(tricarbonylcobaltio)(Co–Co)]germanium (4Co–Ge), [Ge{Co₂(CO)₇}₂]; a new type of group 4–tetracobalt species

    Gerlach, Robert F.; Mackay, Kenneth M.; Nicholson, Brian K.; Robinson, Ward T. (1981)

    Journal article
    University of Waikato

    Reaction between Gel₄ and [Co(CO)₄]⁻ or between GeH₄ and [Co₂(CO)₈] gives [Ge{Co₂(CO)₇}₂](1). The crystal and molecular structure of (1) has been obtained by X-ray methods. Crystals are triclinic, with a= 10.396(2), b= 16.495(3), c= 12.879(2)Å, α= 90.33(2), β= 97.68(2), γ= 95.03(2)°, space group P1, and Z= 4. The structure was solved by direct methods and refined by least-squares techniques to R= 0.056 for 2 852 reflections [I 5σ(l)]. The molecule exhibits approximate C₂ symmetry with the Ge atom bridging the Co–Co bonds of two Co₂(CO)₇ units. The Ge bridge is unsymmetric with unequal Ge–Co bond lengths (average 2.38, 2.34 Å); the corresponding µ-CO in each unit is asymmetrically disposed in the opposite sense. Infrared and mass spectral data for [Ge{Co₂(CO)₇}₂] are also discussed.

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  • 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.

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  • Synthesis and characterization of new trimetallic complexes with {Pt₂Au(μ-S) ₂} ⁿ⁺ (n=2, 3) cores containing C, N and N, N donor ligands

    White, Bradley C.; Henderson, William; Hor, T.S. Andy; Nicholson, Brian K. (2013)

    Journal article
    University of Waikato

    Reactions of the dinuclear platinum(II) sulfide complex [Pt ₂(μ-S) ₂(PPh ₃) ₄] with a range of gold(III) dichloride complexes [AuLCl ₂] containing C, N- or N, N-cycloaurated ligands L gives a new series of dicationic adducts [Pt ₂(μ-S) ₂(PPh ₃) ₄AuL] ²⁺, isolated as their PF ₆ - salts. The complexes investigated are [Au{C₆₋H ₄(CH ₂NMe ₂)-2}Cl ₂], [Au{C ₆H ₃(CH ₂NMe ₂)-2-(OMe)-5}Cl ₂], [Au{NC ₅H ₄(CH ₂C ₆H ₄)-2}Cl ₂], [Au{NC ₅H ₄(COC ₆H ₄)-2}Cl ₂] and [Au{NC ₅H ₄(CONH)-2}Cl ₂]. An X-ray structure determination on the picolinamide-derived complex [Pt ₂(μ-S) ₂(PPh ₃) ₄Au{NC ₅H ₄(CONH)-2}](PF₆) ₂ was not of sufficiently high quality for detailed discussion, but confirmed the atom connectivity. Reactions of [Pt ₂(μ-S) ₂(PPh ₃) ₄] with [AuCl ₂(bipy)]PF ₆ (L=bipy=2,2'-bipyridine) and [AuCl ₂(phen)]Cl (L=phen=1,10-phenanthroline) gives the corresponding tricationic adducts [Pt ₂(μ-S) ₂(PPh ₃) ₄AuL] ³⁺, also isolated as their PF ₆⁻ salts. The complexes are characterised by NMR spectroscopy, electrospray mass spectrometry and microelemental analyses. Biological assay data of a selection of these new complexes towards the P388 murine leukemia cell line, as well as a range of antimicrobial tests, reveals overall low activity compared to other cycloaurated gold(III) complexes.

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  • Influence of chain length on mono- versus di-alkylation in the reactivity of [Pt₂(μ-S)₂(PPh₃)₄] towards α,ω-dihalo-n-alkanes; a synthetic route to platinum(II) ω-haloalkylthiolate complexes

    Devoy, Sarah M.; Henderson, William; Nicholson, Brian K.; Hor, T.S. Andy (2010)

    Journal article
    University of Waikato

    The reactions of [Pt₂(μ-S)₂(PPh₃)₄] with a,x-dibromoalkanes Br(CH₂)nBr (n = 4, 5, 6, 8, 12) gave monoalkylated [Pt₂(μ-S){μ-S(CH₂)nBr}(PPh₃)₄]⁺ and/or di-alkylated [Pt₂(μ-S(CH₂)nS}(PPh₃)₄]²⁺ products, depending on the alkyl chain length and the reaction conditions. With longer chains (n = 8, 12), intramolecular di-alkylation does not proceed in refluxing methanol, with the mono-alkylated products [Pt₂ (μ-S){μ-S(CH₂)nBr}(PPh₃)₄]⁺ being the dominant products when excess alkylating agent is used. The bridged complex [{Pt₂(μ-S)₂(PPh₃)₄}₂{μ-(CH₂)12}]²⁺ was accessible from the reaction of [Pt₂ (μ-S)₂(PPh₃)₄] with 0.5 mol equivalents of Br(CH₂)12Br. [Pt₂(μ-S){μ-S(CH₂)₄Br}(PPh₃)₄]⁺ can be cleanly isolated as its BPh₄⁻ salt, but undergoes facile intramolecular di-alkylation at -18 degree C, giving the known species [Pt₂(μ-S(CH₂)₄S}(PPh₃)₄]²⁺. The reaction of I(CH₂)₆I with [Pt₂(μ-S)₂(PPh₃)₄] similarly gives [Pt₂ (μ-S){μ-S(CH₂)₆I}(PPh₃)₄]⁺, which is fairly stable towards intramolecular di-alkylation once isolated. These reactions provide a facile route to x-haloalkylthiolate complexes which are poorly defined in the literature. X-ray crystal structures of [Pt₂(μ-S){μ-S(CH₂)₅Br}(PPh₃)₄]BPh₄ and [Pt₂(μ-S(CH₂)₅S} (PPh₃)₄](BPh₄)₂ are reported, together with a study of these complexes by electrospray ionisation mass spectrometry. All complexes fragment by dissociation of PPh₃ ligands, and the bromoalkylthiolate complexes show additional fragment ions [Pt₂(μ-S){μ-S(CH₂)n_2CH=CH₂}(PPh₃)m]⁺ (m = 2 or 3; m – 4), most significant for n = 4, formed by elimination of HBr.

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  • Synthesis and characterisation of four- and eight-membered ring auralactam complexes

    Henderson, William; Nicholson, Brian K.; Oliver, Allen G. (2001-02-01)

    Journal article
    University of Waikato

    The reactions of the cyclo-aurated gold(III) dihalide complex [{C6H3 (CH2NMe2)-2-(OMe)-5}AuCl2] with N-cyanoacetylurethane [NCCH2C(O)NHCO2Et], 2-benzoylacetanilide [PhC(O)CH2C(O)NHPh] and acetoacetanilide [MeC(O)CH2C(O)NHPh], and [{C6H4 (CH2NMe2)-2}AuCl2] with acetoacetanilide in dichloromethane with excess silver(I) oxide gives the first examples of auralactam complexes, containing Au-NR-C(O)-CHR′ four-membered rings. A single-crystal X-ray diffraction study on the complex [{C6H4 (CH2NMe2)-2}Au{NPhC(O)CH(COMe)}] reveals similar structural features to related metallalactam complexes of platinum(II) and palladium(II). When a CDCl3 solution of the complex [{C6H3 (CH2NMe2)-2-(OMe)-5}Au{N(CO2Et)C(O)CHCN}] is allowed to stand for 18 h, a novel dimerisation reaction occurs, giving the insoluble product [{C6H3 (CH2NMe2)-2-(OMe) 5}Au{N(CO2Et)C(O)CHCN}]2 2CDCl3, characterised by an X-ray structure determination. The dimer contains an eight-membered Au-N-C(O)-C-Au-N-C(O)-C ring.

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  • Camphene-derived primary and hydroxymethyl phosphines

    Berrigan, Rebecca A.; Russell, Douglas K.; Henderson, William; Leach, Meto T.; Nicholson, Brian K.; Woodward, Gary; Harris, Christopher (2001-01-01)

    Journal article
    University of Waikato

    Thermal disproportionation of (2,2-dimethylbicyclo[2.2.1]hept-3-ylmethyl)phosphinic acid (endo-8-camphanylphosphinic acid, camPO₂H₂) yields the primary phosphine (2,2-dimethylbicyclo[2.2.1]hept-3-ylmethyl)phosphine (camPH₂). The compound has been characterised by NMR spectroscopy, and as its tris(hydroxymethyl)phosphonium chloride salt [camP(CH₂OH)₃]Cl, synthesised by reaction with excess formaldehyde and hydrochloric acid. The X-ray crystal structure of this phosphonium salt is reported, confirming the endo position of the phosphonium group. On treatment with triethylamine base, camP(CH₂OH)₃ ⁺Cl⁻ is converted to the hydroxymethylphosphine camP(CH₂OH)₂. The sulfide and selenide of this phosphine have been prepared, together with the platinum(II) complex cis-[PtCl₂{camP(CH₂OH)₂}₂]. The gas-phase decomposition of camPH₂ has been investigated using the technique of IR laser powered homogeneous pyrolysis. Results indicate the initial elimination of phosphine, followed by the rearrangement and decomposition of camphene through two distinct pathways.

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  • Substituted phenylarsonic acids; structures and spectroscopy

    Lloyd, Nicholas C.; Morgan, Hugh W.; Ronimus, Ron S.; Nicholson, Brian K. (2008)

    Journal article
    University of Waikato

    Full NMR and ESI-MS spectra, and differential scanning calorimeter data are presented for 15 substituted phenylarsonic acids, including two new fluoro-substituted examples. X-ray crystal structure determinations of five examples (phenylarsonic acid and the 4-fluoro-, 4-fluoro-3-nitro-, 3-amino-4-hydroxy- and 3-amino-4-methoxy-substituted derivatives) were determined and the H-bonding crystal-packing patterns analysed.

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  • 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.

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  • The arylation of [Pt₂(μ-S)₂(PPh₃)₄]

    Deadman, Benjamin Jade; Henderson, William; Nicholson, Brian K.; Petchell, Laura Eleanor; Rose, Sarah L.; Hor, T.S. Andy (2009)

    Journal article
    University of Waikato

    Routes to the synthesis of the mixed sulfide-phenylthiolate complex [Pt₂(μ-S)(μ -SPh)(PPh₃)₄]⁺ have been explored; reaction of [Pt₂(μ-S)₂(PPh₃)₄] with excess Ph₂IBr proceeds readily to selectively produce this complex, which was structurally characterised as its PF₆⁻ salt. Reactions of [Pt₂(μ-S)₂(PPh₃)₄] with other potent arylating reagents (1-chloro-2,4-dinitrobenzene and 1,5-difluoro-2,4-dinitrobenzene) also produce the corresponding nitroarylthiolate complexes [Pt₂(μ-S){μ -SC₆H₂(NO₂)₂X}(PPh₃)₄]⁺ (X = H, F). The complex [Pt₂(μ-S)(μ -SPh)(PPh₃)₄]⁺ reacts with Me₂SO₄ to produce the mixed alkyl/aryl bis-thiolate complex [Pt₂(μ-SMe)(μ -SPh)(PPh₃)₄]²⁺, but corresponding reactions with the nitroarylthiolate complexes are plagued by elimination of the nitroaryl group and formation of [Pt₂(μ-SMe)₂(PPh₃)₄]²⁺. [Pt₂(μ-S)(μ -SPh)(PPh₃)₄]⁺ also reacts with Ph₃PAuCl to give [Pt₂(μ-SAuPPh₃)(μ -SPh)(PPh₃)₄]²⁺.

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  • Synthesis and characterization of nickel(II) maltolate complexes containing ancillary bisphosphine ligands

    Alblawi, Jamal; Henderson, William; Nicholson, Brian K. (2011)

    Journal article
    University of Waikato

    Cationic nickel(II) complexes containing chelating O,O'-donor maltolate or ethyl maltolate ligands in conjunction with bidentate bisphosphine ligands Ph₂P(CH₂)nPPh₂ were prepared by a one-pot reaction starting from nickel(II) acetate, bisphosphine, maltol (or ethyl maltol), and trimethylamine, and isolated as their tetraphenylborate salts. An X-ray structure determination of [Ni(maltolate)(Ph₂PCH₂CH₂PPh₂)]BPh₄ shows that the maltolate ligand binds asymmetrically to the (slightly distorted) square-planar nickel(II) center. The simplicity of the synthetic method was extended to the synthesis of the known platinum(II) maltolate complex [Pt(maltolate)(PPh₃)₂]BPh₄ which was obtained in high purity.

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  • Further studies on the dialkylation chemistry of [Pt₂(μ-S)₂(PPh₃)₄] with activated alkyl halides RC(O)CH₂X (X = Cl, Br)

    Ujam, Oguejiofo Theophilus; Henderson, William; Nicholson, Brian K.; Hor, T.S. Andy (2011)

    Journal article
    University of Waikato

    Further studies have been carried out into the reactivity of [Pt₂(μ-S)₂(PPh₃)₄] towards a range of activated alkylating agents of the type RC(O)CH₂X (R = organic moiety e.g. phenyl, pyrenyl; X = Cl, Br). Alkylation of both sulfide centres is observed for PhC(O)CH₂Br, 3-(bromoacetyl)coumarin [CouC(O)CH₂Br], and 1-(bromoacetyl)pyrene [PyrC(O)CH2Br], giving dications [Pt₂{μ-SCH₂C(O)R}₂ (PPh₃)₄] ²⁺, isolated as their PF₆⁻ salts. The X-ray structure of [Pt₂{μ-SCH₂C(O)Ph}₂ (PPh₃)₄](PF₆) ₂ shows the presence of short Pt•••O contacts. In contrast, the corresponding chloro compounds [typified by PhC(O)CH₂Cl] and imino analogues [e.g. PhC(NOH)CH₂Br] do not dialkylate [Pt₂ (μ-S)₂(PPh₃)₄]. The ability of PhC(O)CH₂Br to dialkylate [Pt₂(μ-S)₂(PPh₃)₄] allows the synthesis of new mixed-alkyl dithiolate derivatives of the type [Pt₂{μ-SCH₂C(O)Ph}(μ-SR)(PPh₃)₄]²⁺ (R = Et or n-Bu), through alkylation of in situ-generated monoalkylated compounds [Pt₂(μ-S)(μ-SR)(PPh₃)₄]⁺ (from [Pt₂(μ-S)₂(PPh₃)₄] and excess RBr). In these heterodialkylated systems ligand replacement of PPh₃ occurs by the bromide ions in the reaction mixture forming monocations [Pt₂{μ-SCH₂C(O)Ph}(μ-SR)(PPh₃)₃Br]⁺. This ligand substitution can be easily suppressed by addition of PPh₃ to the reaction mixture. The complex [Pt₂{μ-SCH₂C(O)Ph}(μ-SBu)(PPh₃)₄]²⁺ was crystallographically characterised. X-ray crystal structures of the bromide-containing complexes [Pt₂{μ-SCH₂C(O)Ph}(μ-SR)(PPh₃)₃Br]+ (R = Et, Bu) are also reported. In both structures the coordinated bromide is trans to the SCH₂C(O)Ph ligand, which adopts an axial position, while the ethyl and butyl substituents adopt equatorial positions, in contrast to the structures of the dialkylated complexes [Pt₂{μ-SCH₂C(O)Ph}₂(PPh₃)₄]²⁺ and [Pt₂{μ-SCH₂C(O)Ph}(μ-SBu)(PPh₃)₄]²⁺ (and many other known analogues) where both alkyl groups adopt axial positions.

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  • Further studies on the chemistry of molybdenyl adducts of [Pt₂(μ-S)₂(PPh₃)₄]: Hydrolysis, condensation and ligand exchange processes

    Henderson, William; Nicholson, Brian K.; Bridson, James Hadley; Kueh, Jui Thiang (2011)

    Journal article
    University of Waikato

    Reaction of [Pt₂(μ-S)₂(PPh₃)₄] with [MoO₂(acac)₂] in methanol gives the known five-coordinate Mo(VI) adduct [Pt₂(μ-S)₂(PPh₃)₄MoO₂(OMe)]⁺ isolated as its PF₆⁻, BPh₄⁻ and [Mo₈O₂₆]₄⁻ salts; the latter was structurally characterised, the polymolybdate anion being the uncommon γ form. Hydrolysis of [Pt₂(μ-S)₂(PPh₃)₄MoO₂(OMe)]⁺ in wet dichloromethane initially produces [Pt₂(μ-S)₂(PPh₃)₄MoO₂(OH)]⁺ and subsequently the bright yellow oxo-bridged dimolybdenum species [{Pt₂(μ-S)₂(PPh₃)₄MoO₂}₂O]₂⁺, structurally characterised as its tetraphenylborate salt, and found to contain two five-coordinate molybdenum centres. [{Pt₂(μ-S)₂(PPh₃)₄MoO₂}₂O]₂⁺ can be prepared directly from [Pt₂(μ-S)₂(PPh₃)₄] and [MoO₂(acac)₂] in wet MeCN. Slow reconversion to [Pt₂(μ-S)₂(PPh₃)₄MoO₂(OMe)]⁺ occurs when [{Pt₂(μ-S)₂(PPh₃)₄MoO₂}₂O]₂⁺ is dissolved in methanol. [Pt₂(μ-S)₂(PPh₃)₄MoO₂(OMe)]⁺ undergoes alkoxide exchange in dichloromethane-alcohol solutions to give [Pt₂(μ-S)₂(PPh₃)₄MoO₂(OR)]⁺ species (R = e.g. n-octyl). These reactions are easily monitored using electrospray ionisation mass spectrometry.

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