128 results for Boyd, Peter, Journal article

  • Diboryl and diboranyl porphyrin complexes: Synthesis, structural motifs and redox chemistry: Diborenyl porphyrin or diboranyl isophlorin?

    Weiss, A; Hodgson, MC; Boyd, Peter; Siebert, W; Brothers, Penelope (2007-01)

    Journal article
    The University of Auckland Library

    The syntheses of diboryl porphyrin complexes [(BX2)(2)(ttp)] (ttp: dianion of tetra-p-tolylporphyrin) and the B-B single-bond diboranyl complexes [(BX)(2)(ttp)] (X=F, Cl, Br, I) are given. The former are prepared from the reactions of BX3 (X=F, Cl) with [Li-2(ttp)] and the latter from B2Cl4 (X=Cl), the reaction of SbF3 with [(BCl)(2)(ttp)] (for X=F), and, in the cases of X=Br or I, in a remarkable reductive coupling reaction resulting directly from the reaction of BBr3 or BI3 with [Li-2(ttp)]. Density functional theory (DFT) calculations on the thermochernical parameters for the reductive coupling reactions (and those calculated for related dipyrromethene complexes) indicate that a combination of the reducing ability of bromide and iodide ions combined with the constrained environment of the porphyrin ligand contribute to the driving force. The reductive coupling is also observed in the reaction of [(BCl2)(2)(ttp)] with nBuLi to give [(BnBU)(2)(ttp)], which was characterised crystallographically. The reaction of [(BCl)(2)(ttp)] with catechol gives a boron catecholato porphyrin complex, [B-2(O2C6H4)(ttp)] Chloride abstraction from [(BCl)(2)(ttp)] gives the planar dication [B-2(ttp)](2+), whereas chemical reduction of [(BCl)(2)-(ttp)] by using magnesium anthracenide gives a neutral complex, [B-2(ttp)], in which the ttp ligand has been reduced by two electrons to give an unusual example of an isophlorin complex. The cationic and neutral complexes [B-2(ttp)](2+) and [B-2(ttp)] were characterised through a combination of spectroscopic data that is supported by DFT calculations on the porphine analogues.

    View record details
  • Supramolecular fullerene-porphyrin chemistry. Fullerene complexation by metalated "jaws porphyrin" hosts

    Sun, D; Tham, FS; Reed, CA; Chaker, L; Boyd, Peter (2002)

    Journal article
    The University of Auckland Library

    Porphyrins and fullerenes are spontaneously attracted to each other. This new supramolecular recognition element is explored in discrete, soluble, coordinatively linked porphyrin and metalloporphyrin climers, Jawlike clefts in these bis-porphyrins ar

    View record details
  • BUCKMINSTERFULLERIDE(1-) SALTS - SYNTHESIS, EPR, AND THE JAHN-TELLER DISTORTION OF C-60-

    STINCHCOMBE, J; PENICAUD, A; BHYRAPPA, P; Boyd, Peter; REED, CA (1993-06-16)

    Journal article
    The University of Auckland Library

    Synthetic methods are reported for the isolation of a number of buckminsterfulleride(1-) salts. Counterions include cobaltocenium ion, Na(dibenzo-18-crown-6)+, and bis(N-methylimidazole)(tetraphenylporphinato)tin(IV)2+. The EPR spectrum of C60- in frozen solution shows two unusual features. First, there is a counterion-dependent anisotropy observed at low temperatures. This is ascribed to an ellipsoidal distortion induced by ion pairing. It is consistent with, but not directly ascribable to, a static Jahn-Teller distortion. Second, there are two components to the high-temperature spectrum: the broad essentially Isotropic, major signal and a narrower "spike". The narrower signal is ascribed to thermal population of a low-lying excited state, a natural consequence of the distortion that splits the 2T1u state into closely spaced 2E and 2A states. In contrast to intuition and to ab initio calculations, the 2E state is lowest in most systems studied to date.

    View record details
  • SYNTHESIS AND ELECTRONIC CHARACTERIZATION OF DISCRETE BUCKMINSTERFULLERIDE SALTS - C-60(2-) AND C-60(3-)

    BHYRAPPA, P; PAUL, P; STINCHCOMBE, J; Boyd, Peter; REED, CA (1993-11-17)

    Journal article
    The University of Auckland Library

    Exceptional ball-to-ball interactions between fulleride ions are the basis of superconductivity in alkali-metal-doped c60 and of ferromagnetismZ in [TDAE] [C,]. It is therefore of fundamental...

    View record details
  • SYNTHESIS, STRUCTURE AND MAGNETIC-PROPERTIES OF A LINEAR TRIMANGANESE(III,II,III) COMPLEX BRIDGED WITH A (MU-HYDROXO)BIS(MU-ACETATO) UNIT

    KITAJIMA, N; OSAWA, M; IMAI, S; FUJISAWA, K; MOROOKA, Y; HEERWEGH, K; REED, CA; Boyd, Peter (1994-10-12)

    Journal article
    The University of Auckland Library

    A mixed valence trinuclear manganese(II,III,II) complex [Mn3(admtrz)6(OH)2(DMF)2(H2O)2]2(ClO4)10·2(admtrz)·3H2O (1), (admtrz=4-amino-3,5-dimethyl-1,2,4-triazole) with hydroxo and 1,2,4-triazole as bridging ligands has been isolated, and characterized by X-ray crystallography and magnetic susceptibility measurements. In each cation structure, the central Mn(III) ion lies on an inversion center and is bridged to each of the external Mn(II) ions by one OH− anion and two admtrz ligands. Each external Mn(II) ion completes its octahedral surroundings with one admtrz, one DMF and one H2O molecule. Complex 1 exhibits weak antiferromagnetic coupling. Analysis of variable temperature magnetic susceptibility data (4–300 K) according to a Heisenberg model yields a J value of −4.47 cm−1.

    View record details
  • Role of phosphine ligands in gold cluster chemistry. Relativistic SCF calculations on Au2 and Au2(PH3)2

    Schwerdtfeger, P; Boyd, Peter (1992)

    Journal article
    The University of Auckland Library

    View record details
  • Relativistic effects in gold chemistry. 3. Gold(I) complexes

    Schwerdtfeger, P; Boyd, Peter; Burrell, AK; Robinson, WT; Taylor, MJ (1990)

    Journal article
    The University of Auckland Library

    Geometry-optimized Hartree-Fock (HF) calculations have been carried out for the ground-state properties of linear two-coordinated gold(1) complexes, AuLC (L = H, F, CI, Br, I, CN, SCN, CH3, and PH3+), and for AuCH3, AuPH3, AuPH3+, AuCN, and AuSCN by us ing multielectron adjusted nonrelativistic and relativistic pseudopotentials for the gold atom. Configuration interaction calculations have been performed for the gold(]) halide complexes. The relativistic effects in the Au-L bond are analyzed, and the differences from the corresponding Cu-L and Ag-L bonds are explained. The preference of coordination number 2 in Au(1) is strengthened by relativistic effects. I n contrast to singly bonded AuL species ( J . C h e m . P h y s . 1989, 91, 1762), 5d and 6p contributions to t h e Au-L bond are important in Au(1) complexes. The magnitude of these effects is dependent on the elec- tronegativity of the ligand. Relativistic effects increase gold Sd contributions in the Au-L bond, as expected from the relativistic expansion of the A u Sd orbital and the relativistic contraction of the Au 6 s orbital. I n contrast to the diatomics, no significant relativistic bond destabilization was found for the complex halides. Large relativistic bond stabilizations were obtained for A u ( P H ~ ) ~ + and for Au(CN); ( 8 7 and 39 kJ mol-' per Au-L bond at the H F level, respectively), which account for their high stability compared to the analogous copper or silver compounds. The unusually large negative "CI nuclear quadrupole coupling constant in AuCIY compared with CuCIY and AgCI2- is caused by relativistic effects. Relativistic difference density plots are shown for AuH2-, AuFT, and Au(CN)<. AuSCN and Au(SCN)Y are predicted to have a bent Au-S-C conformation. Since structural data on Au(SCN)Y were not available, we have synthesized [ A s P ~ ~ ] A u ( S C N ) ~ and analyzed this compound by infrared and Raman spectroscopy and have determined its structure by single-crystal X-ray diffraction. These studies confirm the calculated nonlinear Au-S-C arrangement of t h e Au(SCN)Y ion.

    View record details
  • An SCV-MS-Xα study of the bonding and nuclear quadrupole coupling in oxygen compounds of the halogens

    Bowmaker, Graham; Boyd, Peter (1989)

    Journal article
    The University of Auckland Library

    SCF-MS-Xα calculations of the electronic structure of the oxy-halogen compounds Cl2O, ClO, ClO2, ClO2−, ClO3−, ClO4−, BrO, BrO2, BrO3−, IO3−, and IO4− have been used to investigate the bonding and nuclear quadrupole coupling in these molecules and ions. The halogen d orbital participation in the bonding increases with increasing oxidation number of the halogen atom in the molecule or ion. The inclusion of the halogen d orbitais results in an increase in the principal component of the halogen electric field gradient tensor, but only in some cases this result in improved agreement between the calculated and observed halogen nuclear quadrupole coupling constants. In other cases better agreement is obtained for calculations involving the halogen p orbitais only in the valence shell. Thus the results do not provide unambiguous evidence for the involvement of halogen d orbitais in the bonding. In the case of the ClO3− and BrO3− ions for which 17O quadrupole coupling constants have been reported, the Xα values have been calculated. Agreement between the calculated and observed values is much poorer than for the halogen coupling constants. The results of the calculations have also been used to investigate some of the approximations made in the Townes and Dailey method of analysis of nuclear quadrupole coupling data.

    View record details
  • Potential building blocks for molecular ferromagnets: [Mn12O12(O2CPh)16(H2O)4] with a S = 14 ground state

    Boyd, Peter; Li, Q; Vincent, JB; Folting, K; Chang, HR; Streib, WE; Huffman, JC; Christou, G; Hendrickson, DN (1988)

    Journal article
    The University of Auckland Library

    View record details
  • SYNTHETIC, STRUCTURAL, AND THEORETICAL-STUDIES ON THE ELECTRON-DEFICIENT CUBANES (RC5H4)4TI4S4, (RC5H4)4V4S4, AND [(RC5H4)4V4S4]+

    DARKWA, J; LOCKEMEYER, JR; Boyd, Peter; RAUCHFUSS, TB; RHEINGOLD, AL (1988-01-06)

    Journal article
    The University of Auckland Library

    Treatment of (MeCp),V,S4 with PBu, gives the electron-deficient (56e) cubane (MeCp),V4S4 (1). Desulfurization of a 1:l mixture of (MeCp),V,S, and Cp2V2S4 gave a mixture of ring-substituted cubanes (MeCp),,Cp,V4S4 ( x = 1-4) while (MeCp),V,S, and Cp2V react to give exclusively (MeCp),Cp2V4S4. Compound 1 has a triplet ( S = 1) ground state, exhibits Curie-Weiss magnetic behavior, and has a well-resolved isotropically shifted 'H NMR spectrum. Cyclic voltammetry (vs Ag/AgCl) established the following redox series: 1+/1 (772 mV), 1/1- (176 mV), and 1-/1*- (-1281 mV). The salt [l](BF,) was prepared by the reaction of 1 and Ph3CBF4. The diamagnetic 52e cubanes (RCp),Ti4S4 (R = Me (2), i-Pr) were prepared from (RCp)TiCI,(THF), and (Me,Si),S. The compounds 1, [1](BF4), and 2 were characterized by single-crystal X-ray diffraction. Compound 1 crystallized in the cubic space group P43n with a = 16.551 ( 3 ) A with Z = 6; 671 unique reflecti_ons were processed to a final R ( F ) = 5.31 (R,(F) = 5.80). Compound [1](BF4) crystallized in the tetragonal space group I4 with a = 10.600 (3) A and c = 12.600 ( 3 ) A with Z = 2; 463 unique reflections were processed to a final R = 6.40 (R,(F) = 6.55). Compound 2 crystallized i n the orthorhombic space group Cmca with a = 1.412 (5), b = 17.293 (6), c = 24.503 ( 9 ) %, with Z = 8; 558 unique reflections were processed to give R = 10.5 (R,(F) = 12.6). 1 and [1]+ are extremely similar structurally; no bond distances differ by more than 0.03 A. The structure of 2 revealed two sets of Ti-Ti distances, four distances of 3.00 %, and two of 2.93 A. Electronic structure calculations of Cp4V4S4 and [Cp4V4S4]+ were performed by the scattered wave-Xa method. The ground-state configuration for the Cp4V4S4 metal bonding orbitals is a,2e4t22. The t2 orbital is predicted to be nonbonding, consistent with the structural results. The bonding i n 1, 1+, and 2 is discussed i n light of recent results from other laboratories

    View record details
  • An SCF-Xα scattered wave study of the electronic structure and iron quadrupole splitting in the [Fe(MoS4)Cl2]2− ion

    Boyd, Peter (1987-07)

    Journal article
    The University of Auckland Library

    Spin restricted and spin polarised SCF MS-Xα calculations have been performed to investigate the electronic structure and iron nuclear quadrupole coupling tensor of the [Fe(MoS4)Cl2]2− dianion. It is found that both the spin restricted and spin polarised models predict a ground state quintet (S = 2) in agreement with that observed experimentally with similar overall charge distributions. However the calculated quadrupole coupling tensor varies in magnitude and sign between the two calculations. The spin polarised calculation gives values of the quadrupole coupling tensor that agree well both in magnitude, sign, and direction with those reported from single crystal Mössbauer spectroscopy. The principal direction of the electric field gradient tensor is found to be sensitive to the relative occupations of the iron dz2 and dx2-y2 orbitals (which are mixed under C2V symmetry).

    View record details
  • BIS-BENZIMIDAZOLE-APPENDED BINUCLEATING PORPHYRIN LIGANDS - SYNTHESIS, CHARACTERIZATION, AND X-RAY STRUCTURE

    LARSEN, NG; Boyd, Peter; RODGERS, SJ; WUENSCHELL, GE; KOCH, CA; RASMUSSEN, S; TATE, JR; ERLER, BS; REED, CA (1986-10-29)

    Journal article
    The University of Auckland Library

    The synthesis and characterization of some new binucleating tetraarylporphyrin ligands is reported. The potentially most useful example is α,α,5,15-bis[N-(2-methylbenzimidazolyl)acetamidophenyl]-α, α,10,20-bis(pivalamidophenyl)porphine (8). The ligands have two appended benzimidazole arms which are designed to chelate a second metal directly above the porphyrin. The synthetic methodology for obtaining both the 5,15 (i.e., trans) and the 5,10 (i.e., cis) bis-appended ligand from an α, α, α, α,5,10,15,20 tetra-functionalized starting material is described in detail. A key design feature of the ligand system is amenability to single-crystal X-ray structure determination and this is demonstrated with an X-ray structure of a copper(II) complex. Crystal data for CuC74H66N12O4·1.5(diethyl ether)·toluene are the following: monoclinic, C2/c, a = 31.240 (4) Å, b = 16.769 (5) Å, c = 35.199 (4) Å, β = 121.4 (1)°; R = 0.0823, Rw = 0.0826. H bonding between the benzimidazole moieties and the pivalamido pickets is seen to determine the structural disposition of the appendages lying above the porphyrin ring. Iron(III) porphyrin complexes of these new ligands exist in a hydroxo monomer form as well as the familiar μ-oxo dimer form.

    View record details
  • SPIN SPIN INTERACTIONS IN POLYNUCLEAR NICKEL(II) COMPLEXES - A LOW-TEMPERATURE SUSCEPTIBILITY AND MAGNETIZATION STUDY OF THE CUBANE TETRANUCLEAR COMPLEX NI4(II)(CYCLOHEXANE-R-1,C-3,C-5-TRIAMINE)4(MU-OH)4(NO3)4.7H2O

    Boyd, Peter; MARTIN, RL; SCHWARZENBACH, G (1988-01-01)

    Journal article
    The University of Auckland Library

    The bulk magnetic susceptibility of the complex Ni4(chta)4(μ-OH)4(NO3)4.7H2O ( chta = cyclohexane-r-1,c-3,c-5-triamine) has been measured over the temperature range from 1.9 to 300 K at a field of 1 T. The observed data were fitted by a Heisenberg exchange model for the susceptibility of a cubane [Ni4II(μ-OH)4]4+ cluster with a single exchange interaction J between each pair of NiII ions for a single ion g value 2.20 and an antiferromagnetic spin-spin coupling parameter 2J = -1.14 cm-1. The bulk magnetization measured at fields of 1 to 5 T in the temperature range from 5 to 1.9 K differed from that calculated from the simple Heisenberg model above. Several possibilities were examined for this deviation including intercluster interactions, single ion zero-field splitting and differing exchange coupling constants between nickel(II) ions in the cluster. This last model was successful in describing the complete set of magnetic data. A comparison with other known oxygen-bridged nickel(II) cubane clusters shows a change from antiferromagnetic to ferromagnetic coupling as the Ni-O-Ni bond angle decreases. It appears that the cubane cluster studied here is in a region very close to the crossover from antiferromagnetic to ferromagnetic coupling between the nickel ions.

    View record details
  • Valence trapping in mixed-valence MnIIMnIII complexes of a macrocyclic binucleating ligand

    Chang, HR; Larsen, SK; Boyd, Peter; Pierpont, CG; Hendrickson, DN (1988)

    Journal article
    The University of Auckland Library

    The electronic structures of two mixed-valence MnMn complexes, [LMnClBr]·HO (2) and [LMnBr]·1/2CHCl (3), and the Mn complex LMnCl (4) are probed. The L ligand is the dianion of the Schiff base condensation of 2 mol of 1,3-diaminopropane and 2 mol of 2,6-diformyl-4-tert-butylphenol. The X-ray structure of complex 4 has been determined by using direct methods to give discrepancy factors of R = 0.0501 and R = 0.0697 for 1884 observed (|F| > 6.0σ|F|) reflections. Complex 4 crystallizes in the triclinic space group P1 with one molecule in a unit cell with dimensions a = 7.270 (1) Å, b = 9.457 (2) Å, c = 12.316 (2) Å, α = 108.36 (1)°, β = 94.92 (1)°, and γ = 99.58 (1)°. The observed and calculated densities are 1.39 (2) and 1.41 g cm, respectively. The L ligand in LMnCl is essentially planar, with the Mn ions displaced by 0.69 Å on either side of the ligand plane. The Mn⋯Mn distance is 3.168 (3) Å. The X-ray structure of complex 2 has been determined by using direct methods to give R = 0.0711 and R = 0.0974 for 1732 observed (|F| > 6.0σ|F|) reflections. Complex 2 crystallizes in the monoclinic space group C2/c with 8 molecules in a unit cell with dimensions a = 21.064 (7) Å, b = 13.559 (4) Å, c = 27.652 (6) Å, and β = 105.51 (2)°. The observed and calculated densities are 1.38 (2) and 1.34 g cm. The structural results for [LMnClBr]·HO show that this complex is valence trapped. The Mn ion has an average Mn-O length of 1.936 (10) Å, while the Mn ion exhibits Mn-O lengths of 2.129 (10) and 2.386 (11) Å. The Mn ion is coordinated axially to two halide ions and is 0.15 Å out of the ligand-atom plane. The Mn ion is displaced 1.25 A from the ligand-atom plane on the opposite side and interacts with one of the halide ions coordinated to the Mn ion. Electrochemical results are presented for LMnX (X = Cl or Br) to show that these complexes have two one-electron oxidation waves at ca. +0.6 and ca. +1.2 V vs NHE. Variable-temperature magnetic susceptibility data are fit to give magnetic exchange parameters of +0.24, -2, and -1 cm for complexes 4, 2, and 3, respectively. Similar EPR data are found for the two mixed-valence complexes. At 7.5 K a glass of 3 gives an X-band spectrum with a broad g = 2 signal and apparent fine structure signals at g = 29.0, 7.4, 5.4, and 4.1. A combination of Orbach relaxation processes involving low-lying spin states and modulation of the g, g values for the ground doublet by strain effects on the magnitude of the isotropic exchange and/or single-ion zero-field splitting are suggested as the origin of the absence of resolution of manganese hyperfine structure in the g = 2 signal. Relatively weak antiferromagnetic interactions are seen for the five known binuclear MnMn complexes, whereas, strong antiferromagnetic interactions are found for the five known binuclear MnMn complexes. The possible causes of this difference in magnitude of exchange interactions are discussed.

    View record details
  • Crystal, molecular, and electronic structure of [Ta2Cl 4(μ-Cl)4(PMe3)4]: A metal-metal single bond between eight-co-ordinate tantalum atoms

    Boyd, Peter; Jones, TC; Nielson, AJ; Rickard, CEF (1984)

    Journal article
    The University of Auckland Library

    The crystal structure of the title complex shows an MCl4M bridge across a weak Ta–Ta interaction and eight-fold co-ordination about each metal centre; an electronic structure calculation supports the existence of a σ metal–metal bond.

    View record details
  • Extending the Range of Neutral N-Donor Ligands Available for Metal Catalysts: N-[1-Alkylpyridin-4(1H)-ylidene]amides in Palladium-Catalyzed Cross-Coupling Reactions

    Boyd, Peter; Wright, Leonard; Zafar, MN (2011-09)

    Journal article
    The University of Auckland Library

    N-[1-Alkylpyridin-4(1H)-ylidene]amides (PYAs) are a new class of easily prepared, neutral N-donor ligands that share some features in common with N-heterocyclic carbenes. They are strongly electron-donating toward metal centers, and a palladium(II) complex of one of these ligands has been shown to successfully catalyze both the Heck-Mizoroki and Suzuki-Miyaura cross-coupling reactions.

    View record details
  • Ordered structure of a distorted C fulleride ion

    Paul, P; Xie, Z; Bau, R; Boyd, Peter; Reed, CA (1994-05-04)

    Journal article
    The University of Auckland Library

    The discovery of superconductivity’ and ferromagnetism2 in salts of Cw bas focused attention on the electronic and structural properties of fulleride ions, CwF. ...

    View record details
  • Ubiquitous C120O impurity in C-60: The EPR evidence for thermally accessible excited states in C-60(2-) and C-60(3-) fullerides is artifactual.

    Reed, CA; Paul, P; Boyd, Peter (2001)

    Journal article
    The University of Auckland Library

    View record details
  • 5,15-Bis(p-methylphenyl)-2,8,12,18-tetrabutyl-3,7,13,17-tetramethylporphyrin

    Boyd, Peter; Hosseini, Ali (2006)

    Journal article
    The University of Auckland Library

    The centrosymmetric title compound, C54H66N4, is a 5,15 diaryloctaalkyl free base porphyrin. The planar 24-atom porphyrin core has a significant in-plane distortion commonly observed in these types of molecules along the 5,15 direction. The porphyrin molecules are arranged in the crystal structure in two-dimensional assemblies via phenyl-edge-to-porphyrin-face interactions.

    View record details
  • 3-Allyl-2-hydroxy-5,6,8-trimethoxynaphthalene-1,4-dione

    Rathwell, DC; Tsang, Kit; Choi, Ka; Boyd, Peter; Brimble, Margaret (2008)

    Journal article
    The University of Auckland Library

    In the crystal structure of the title compound, C16H16O6, a pair of naphthoquinone rings are linked via O-HO-C hydrogen bonds in a nearly orthogonal arrangement. This dimeric unit is linked to a neighbouring dimer by - stacking interactions between the naphthoquinone rings, where the distance between the mean plane of the naphtoquinone backbones is 3.468 Å, and O-HO-C hydrogen bonds.

    View record details