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  • Conference paper
    Tomov AK, Nobbs JD, Britovsek GJ, Gibson VCet al., 2011,

    Alternating α-olefin distributions in chromium-catalysed ethylene oligomerisation.

    , Publisher: American Chemical Society, Pages: INOR-529

    The last two decades have witnessed tremendous advances in catalyst development for the selective oligomerisation of ethylene.1 The Cossee-type chain growth mechanism results, in the absence of chain termination reactions, in a Poisson distribution of products (e.g. Alfen process). A combination of chain propagation and chain termination, for example β-H transfer, results in a Schulz-Flory distribution of α-olefins, (e.g. Shell Higher Olefin Process). An alternative chain growth mechanism based on the formation of metallacycles has enabled the selective trimerisation and tetramerisation of ethylene or the formation of higher oligomers. We have previously communicated an exceptionally active chromium-based catalyst supported by a tridentate bis(benzimidazolyl)amine ligand that affords a previously unobserved alternating α-olefin distribution, as shown below.2 Further studies on this remarkable catalyst system as well as mechanistic implications for olefin polymn. catalysis will be presented. Refernces 1)McGuinness, D. Rev., 2011, 111 ,2321. 2)Tomov, A.K.; Chirinos, J.J.; Long, R.; Gibson, V.C.; Elsegood. 2006, 128, 7704. [on SciFinder(R)]

  • Journal article
    Conifer CM, Law DJ, Sunley GJ, White AJP, Britovsek GJPet al., 2011,

    Lewis Acids and Lewis Acid-Functionalized Ligands in Rhodium-Catalyzed Methyl Acetate Carbonylation

    , Organometallics, Vol: 30, Pages: 4060-4066-4060-4066
  • Journal article
    Whiteoak CJ, de Rosales RTM, White AJP, Britovsek GJPet al., 2010,

    Iron(II) Complexes with Tetradentate Bis(aminophenolate) Ligands: Synthesis and Characterization, Solution Behavior, and Reactivity with O-2

    , INORGANIC CHEMISTRY, Vol: 49, Pages: 11106-11117, ISSN: 0020-1669
  • Journal article
    Cariou R, Chirinos JJ, Gibson VC, Jacobsen G, Tomov AK, Britovsek GJP, White AJPet al., 2010,

    The effect of the central donor in bis(benzimidazole)-based cobalt catalysts for the selective cis-1,4-polymerization of butadiene.

    , Dalton Trans., Vol: 39, Pages: 9039-9045, ISSN: 1477-9226

    A series of bis(benzimidazole)-based cobalt(ii) dichloride complexes contg. a range of different central donors has been synthesized and characterized. The nature of the central donor affects the binding of the ligand to the cobalt center and dets. the coordination geometry of the metal complexes. All complexes have been shown to catalyze the polymn. of butadiene, in combination with MAO as the co-catalyst, to give cis-1,4-polybutadiene with high selectivity. The nature of the central donor has a marked influence on the polymn. activity of the catalysts, but does not affect the polymer microstructure. The addn. of PPh3 generally increases the polymn. activity of these cobalt catalysts and results in predominantly (60-70%) 1,2-vinyl-polybutadiene. [on SciFinder(R)]

  • Journal article
    Lyakin OY, Bryliakov KP, Britovsek GJP, Talsi EPet al., 2009,

    EPR Spectroscopic Trapping of the Active Species of Nonheme Iron-Catalyzed Oxidation

    , JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, Vol: 131, Pages: 10798-+, ISSN: 0002-7863
  • Journal article
    England J, Gondhia R, Bigorra-Lopez L, Petersen AR, White AJP, Britovsek GJPet al., 2009,

    Towards robust alkane oxidation catalysts: electronic variations in non-heme iron(II) complexes and their effect in catalytic alkane oxidation

    , DALTON TRANSACTIONS, Pages: 5319-5334, ISSN: 1477-9226
  • Journal article
    Whiteoak CJ, Britovsek GJP, Gibson VC, White AJPet al., 2009,

    Electronic effects in oxo transfer reactions catalysed by salan molybdenum(VI) cis-dioxo complexes

    , DALTON TRANSACTIONS, Pages: 2337-2344, ISSN: 1477-9226
  • Journal article
    Taylor RA, Law DJ, Sunley GJ, White AJP, Britovsek GJPet al., 2009,

    Towards Photocatalytic Alkane Oxidation: The Insertion of Dioxygen into a Platinum (II)-Methyl Bond

    , ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, Vol: 48, Pages: 5900-5903, ISSN: 1433-7851
  • Journal article
    Tomov AK, Gibson VC, Britovsek GJP, Long RJ, van Meurs M, Jones DJ, Tellmann KP, Chirinos JJet al., 2009,

    Distinguishing Chain Growth Mechanisms in Metal-catalyzed Olefin Oligomerization and Polymerization Systems: C2H4/C2D4 Co-oligomerization/Polymerization Experiments Using Chromium, Iron, and Cobalt Catalysts.

    , Organometallics, Vol: 28, Pages: 7033-7040, ISSN: 0276-7333

    A series of co-oligomerization and copolymn. reactions of C2H4/C2D4 (1:1) mixts. have been carried out using various transition metal catalysts based on Cr, Co, and Fe in combination with MAO. The oligomeric α-olefin products have been analyzed by GC and GC/MS, and the exptl. results have been compared with the theor. mass spectra derived from math. models. Solid polymer samples have been analyzed by 13C{1H} and 13C DEPT-135 NMR spectroscopy. C2H4/C2D4 co-oligomerization can be used as a method to differentiate between a metallacyclic or a Cossee-type chain growth mechanism in oligomerization systems. In the case of a metallacyclic mechanism, no H/D scrambling is obsd., whereas for a Cossee-type mechanism, similar rates of chain propagation and chain termination (β-H elimination) result in rapid H/D scrambling of the C2H4/C2D4 feed. This method is therefore limited to oligomerization systems and cannot be applied in polymn. systems, where the rate of chain propagation is much faster than the rate of chain termination. [on SciFinder(R)]

  • Journal article
    Nobbs JD, Gibson VC, Britovsek GJP, Tomov AKet al., 2009,

    2,6-Bis(thiazolyl)pyridine ligands and their Cr(III), Mn(II), Fe(II), Co(II) and Ni(II) complexes: Effect of metal upon olefin and diolefin polymerization.

    , Abstract of Papers, 238th ACS National Meeting, Washington, DC, United States, August 16-20, 2009, Pages: INOR-714

    A range of transition metal complexes (CrIII, MnII, FeII, CoII and NiII) bearing tridentate thiazoline ligands have been synthesized. The structure of the ligand was varied by changing the thiazoline ring substituents R. The synthesis and characterization of these complexes will be described and the effect of the ligand on the coordination geometry of the complexes will be discussed. The complexes have been used as catalysts in butadiene polymn. and ethylene oligomerisation. The effect of the metal and the ligand on the polymn. behavior of the catalysts has been investigated. [on SciFinder(R)]

  • Journal article
    Nagy M, David K, Britovsek GJP, Ragauskas AJet al., 2009,

    Catalytic hydrogenolysis of ethanol organosolv lignin.

    , Holzforschung, Vol: 63, Pages: 513-520, ISSN: 0018-3830

    The prodn. of ethanol based on lignocellulosic materials will bring about the coprodn. of significant amts. of under-utilized lignin. This study examines the potential of conventional heterogeneous and novel homogeneous catalysts for the selective cleavage of the aryl-O-aryl and aryl-O-aliph. linkages of ethanol organosolv lignin to convert it from a low grade fuel to potential fuel precursors or other value added chems. The development of hydrogenolysis conditions that effectively increase the soly. of lignin were initially examd. with Ru(Cl)2(PPh3)3 and demonstrated the ability to decrease the mol. wt. and enhance the soly. of the lignin polymer. Later studies examd. several heterogeneous and homogeneous hydrogenation catalysts at optimized reaction conditions resulting in 96.4% soly. with Ru(Cl)2(PPh3)3, increase in H/C ratio with Raney-Ni, Pt/C and extensive monomer formation with NaBH4/I2. The changes in mol. structure of lignin were followed by size exclusion chromatog., qual. and quant. NMR spectroscopy and elemental anal. These studies demonstrated that aryl-O-aryl and aryl-O-aliph. linkages could be cleaved and the hydrogenated lignin had a decrease in oxygen functionality and the formation of products with lower oxygen content. [on SciFinder(R)]

  • Conference paper
    Nagy M, Britovsek GJP, Ragauskas AJ, 2008,

    Unleashing organosolv lignin for biofuels

    , ISSN: 0065-7727

    The development of cellulosic ethanol will result in the generation of significant amounts of under-utilized lignin. This research study examines the potential of conventional heterogeneous and novel homogeneous catalysts for the hydrogenation of ethanol organosolv lignin to biofuels. The development of hydrogenolysis conditions that effectively decrease the molecular weight of lignin were initially examined with a B-O-aryl ether lignin model compound. Hydrogenation studies with RhCl(PPh3)3 and Ru(Cl)2(PPh3)3 indicated that the B-O-aryl ether linkage could be cleaved. Applications to lignin demonstrated the ability to decrease the molecular weight and enhance its solubility. The changes in molecular structure of lignin were followed by NMR, GPC and MALDI. These studies demonstrated that the hydrogenated lignin had a decrease in oxygen functionality and the formation of products enriched in H/C. This presentation will summarize our studies at optimizing this reductive treatment to provide a novel route of converting lignin to a biofuel.

  • Conference paper
    Nagy M, Britovsek GJP, Ragauskas AJ, 2008,

    CATL 35-Unleashing organosolv lignin for biofuels

    , 236th National Meeting of the American-Chemical-Society, Publisher: AMER CHEMICAL SOC, ISSN: 0065-7727
  • Journal article
    Taylor RA, Law DJ, Sunley GJ, White AJP, Britovsek GJPet al., 2008,

    Hydrogen bonding directs the H(2)O(2) oxidation of platinum(II) to a cis-dihydroxo platinum(IV) complex

    , CHEMICAL COMMUNICATIONS, Pages: 2800-2802, ISSN: 1359-7345
  • Journal article
    Hellstrom SL, Ugolotti J, Britovsek GJP, Jones TS, White AJPet al., 2008,

    The effect of fluorination on the luminescent behaviour of 8-hydroxyquinoline boron compounds.

    , New J. Chem., Vol: 32, Pages: 1379-1387, ISSN: 1144-0546

    B quinolinate compds. with different degrees of fluorination {Ph2BQ 1, (4-F-C6H4)2BQ 2 and (C6F5)2BQ 3 (Q is 8-quinolinate)} were prepd. and their electronic and luminescent behavior was studied in a variety of org. light emitting device structures. Cyclic voltammetry studies showed a decrease in ionization potential with the degree of fluorination. Electroluminescence (EL) measurements showed increasingly red shifted exciplex emission, originating from the different B compds. interacting with the hole transporting layer. In layered devices, the B compds. 1-3 are inferior in their EL performance compared to Al tris(8-quinolinoate) (AlQ3). However, when the B compds. 1, 2 or 3 are doped into a 4,4'-bis(carbazol-9-yl)diphenyl (CBP) host, emission solely attributable to 1-3 is obsd. In such devices, the B compds. 1 and 2 outperform AlQ3 as an emitter at low to moderate current densities. [on SciFinder(R)]

  • Journal article
    England J, Davies CR, Banaru M, White AJP, Britovsek GJPet al., 2008,

    Catalyst stability determines the catalytic activity of non-heme iron catalysts in the oxidation of alkanes.

    , Adv. Synth. Catal., Vol: 350, Pages: 883-897, ISSN: 1615-4150

    A series of iron(II) bis(triflate) complexes [Fe(L)(OTf)2] contg. linear tetradentate bis(pyridylmethyl)diamine ligands with a range of ligand backbones has been prepd. The backbone of the ligand series has been varied from a two-carbon linkage [ethylene (1), 4,5-dichlorophenylene (2) and cyclohexyl (3)] to a three-carbon [propyl (4)) and a four-carbon linkage (Bu (5)]. The coordination geometries of these complexes have been investigated in the solid state by X-ray crystallog. and in soln. by 1H and 19F NMR spectroscopy. Due to the labile nature of high-spin iron(II) complexes in soln., dynamic equil. of complexes with different coordination geometries (cis-α, cis-β and trans) are obsd. with ligands 2-5. In these cases, the geometry obsd. in the solid state does not necessarily represent the only or even the major geometry present in soln. The ligand field strength in the various complexes has been investigated by variable temp. magnetic moment measurements and UV-vis spectroscopy. The strongest ligand field is obsd. with the most rigid ligands 1 and 2, which generate complexes [Fe(L)(OTf)2] with a cis-α coordination geometry and the corresponding complexes [Fe(L)(CH3CN)2]2+ display spin crossover behavior. The catalytic properties of the complexes for the oxidn. of cyclohexane, using hydrogen peroxide as the oxidant, have been investigated. An increased flexibility in the ligand results in a weaker ligand field, which increases the lability of the complexes. The activity and selectivity of the catalysts appear to be related to the strength of the ligand field and the stability of the catalyst in the oxidizing environment. [on SciFinder(R)]

  • Journal article
    England J, Britovsek GJP, Rabadia N, White AJPet al., 2007,

    Ligand topology variations and the importance of ligand field strength in non-heme iron catalyzed oxidations of alkanes

    , INORGANIC CHEMISTRY, Vol: 46, Pages: 3752-3767, ISSN: 0020-1669
  • Journal article
    Ugolotti J, Hellstrom S, Britovsek GJP, Jones TS, Hunt P, White AJPet al., 2007,

    Synthesis and characterisation of luminescent fluorinated organoboron compounds

    , Dalton Trans., Pages: 1425-1432-1425-1432
  • Journal article
    McTavish S, Britovsek GJP, Smit TM, Gibson VC, White AJP, Williams DJet al., 2007,

    Iron-based ethylene polymerization catalysts supported by bis(imino)pyridine ligands: Derivatization via deprotonation/alkylation at the ketimine methyl position.

    , J. Mol. Catal. A: Chem., Vol: 261, Pages: 293-300, ISSN: 1381-1169

    Bis(imino)pyridine ligands, L [where L = 2,6-(ArNCR1)2C5H3N R1 = Et, iPr, CH2CH2Ph or CH(CH2Ph)2 and Ar = 2,4,6-(Me)3C6H2 (MES) or 2,6-(iPr)2C6H3 (DIPP)] have been prepd. by deprotonation of the parent ketimine ligand (R1 = Me) using lithium diisopropylamide (LDA), followed by alkylation with the appropriate alkylhalide. The corresponding iron dichloride complexes LFeCl2 are highly active ethylene polymn. catalysts upon treatment with methylaluminoxane (MAO), with activities in the range of 3000-18,000 g/mmol bar h. The mol. wts. (Mn) of the resultant polyethylenes lie in the range of 6500-24,000 with broad mol. wt. distributions (16.5-38.0). The nature of the imine carbon substituent has a marked effect on the polymer mol. wt. whereas the catalyst activity is largely unaffected by changes to this substituent. [on SciFinder(R)]

  • Journal article
    Britovsek GJP, Taylor RA, 2006,

    INOR 901-H-bonding effects in alkane oxidation catalysis

    , ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY, Vol: 232, ISSN: 0065-7727
  • Journal article
    Britovsek GJP, England J, 2006,

    INOR 503-Non-heme iron catalysts for the oxidation of alkanes

    , ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY, Vol: 232, ISSN: 0065-7727
  • Journal article
    Britovsek GJP, Taylor RA, Sunley GJ, Law DJ, White AJPet al., 2006,

    Protonation of platinum(II) dialkyl complexes containing ligands with proximate H-bonding substituents

    , ORGANOMETALLICS, Vol: 25, Pages: 2074-2079, ISSN: 0276-7333
  • Journal article
    Britovsek GJP, England J, White AJP, 2006,

    Iron(II), manganese(II) and cobalt(II) complexes containing tetradentate biphenyl-bridged ligands and their application in alkane oxidation catalysis

    , DALTON TRANSACTIONS, Pages: 1399-1408, ISSN: 1477-9226
  • Journal article
    Arthur J Ragauskas, Charlotte K Williams, Brian H Davison, George Britovsek, John Cairney, Charles A Eckert, William J Frederick Jr, Jason P Hallett, David J Leak, Charles L Liotta, Jonathan R Mielenz, Richard Murphy, Richard Templer, Timothy Tschaplinskyet al., 2006,

    The Path Forward for Biofuels and Biomaterials

    , Science, Pages: 484-489
  • Journal article
    Britovsek GJP, Ugolotti J, Hunt P, White AJPet al., 2006,

    Lewis and Bronsted multifunctionality: an unusual heterocycle from the reaction of bis(pentafluorophenyl)borinic acid with nitriles

    , Chem. Commun., Pages: 1295-1297-1295-1297

    The combination of Lewis and Bronsted acidity as well as Lewis basicity in (CF)BOH results in a remarkable reactivity towards organonitriles to give novel heterocyclic compounds containing a BOBOCN six-membered ring.

  • Journal article
    Britovsek GJP, England J, White AJP, 2005,

    Non-heme lron(II) complexes containing tripodal tetradentate nitrogen ligands and their application in alkane oxidation catalysis

    , INORGANIC CHEMISTRY, Vol: 44, Pages: 8125-8134, ISSN: 0020-1669
  • Conference paper
    Britovsek GJP, Ugolotti J, 2005,

    Monodentate and bidentate organoboron Lewis acids

    , 230th National Meeting of the American-Chemical-Society, Publisher: AMER CHEMICAL SOC, Pages: U2219-U2219, ISSN: 0065-7727
  • Conference paper
    Britovsek GJP, England J, 2005,

    Non-heme iron(II) complexes as catalysts for the oxidation of alkanes

    , 230th National Meeting of the American-Chemical-Society, Publisher: AMER CHEMICAL SOC, Pages: U2230-U2230, ISSN: 0065-7727
  • Journal article
    van Meurs M, Britovsek GJP, Gibson VC, Cohen SAet al., 2005,

    Polyethylene chain growth on zinc catalyzed by olefin polymerization catalysts: A comparative investigation of highly active catalyst systems across the transition series

    , JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, Vol: 127, Pages: 9913-9923, ISSN: 0002-7863
  • Journal article
    Britovsek GJP, Ugolotti J, White AJP, 2005,

    From B(C6F5)(3) to B(OC6F5)(3): Synthesis of (C6F5)(2)BOC6F5 and C6F5B(OC6F5)(2) and their relative lewis acidity

    , ORGANOMETALLICS, Vol: 24, Pages: 1685-1691, ISSN: 0276-7333

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