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Tobin J. Marks - One of the best experts on this subject based on the ideXlab platform.

  • pyridylamido bi hafnium olefin Polymerization Catalysis conformationally supported hf hf enchainment cooperativity
    ACS Catalysis, 2015
    Co-Authors: Yanshan Gao, Cristiano Zuccaccia, Alceo Macchioni, Aidan R Mouat, Alessandro Motta, Massimiliano Delferro, Tobin J. Marks
    Abstract:

    Homobimetallic Hf(IV) complexes, L2-Hf2Me5 (3) and L2-Hf2Me4 (4) (L2 = N,N′-{[naphthalene-1,4-diylbis(pyridine-6,2-diyl)]bis[(2-isopropylphenyl)methylene)]bis(2,6-diisopropylaniline}), were synthesized by reaction of the free ligand L2 with the appropriate Hf precursor and were characterized in solution (NMR) and in the solid state (X-ray diffraction). In 3, L2 acts as a dianionic tridentate ligand for one Hf metal center and as a monoanionic bidentate ligand for the other, whereas in 4, both Hf units are tricoordinated to opposite sides of L2. In the solid state, the Hf···Hf distance is significantly different in 3 vs 4 (6.16 vs 8.06 A, respectively), but in solution, the structural dynamics of the two linked metallic units in bis-activated complex 3 accesses conformers with far closer Hf···Hf distances (∼3.2 A). Once activated with Ph3C+B(C6F5)4– (B1) or PhNMe2H+B(C6F5)4– (NB), 3 exhibits pronounced bimetallic cooperative effects in ethylene homoPolymerization and ethylene +1-octene coPolymerization vs ...

  • ni ii phenoxyiminato olefin Polymerization Catalysis striking coordinative modulation of hyperbranched polymer microstructure and stability by a proximate sulfonyl group
    ACS Catalysis, 2014
    Co-Authors: Casey J Stephenson, Changle Chen, Alessandro Motta, Massimiliano Delferro, Jennifer P Mcinnis, Michael P Weberski, Tobin J. Marks
    Abstract:

    The synthesis, structural characterization, and ethylene Polymerization properties of two neutrally charged Ni(II) phenoxyiminato catalysts are compared and contrasted. Complex FI-SO2-Ni features a...

  • ni ii phenoxyiminato olefin Polymerization Catalysis striking coordinative modulation of hyperbranched polymer microstructure and stability by a proximate sulfonyl group
    ACS Catalysis, 2014
    Co-Authors: Casey J Stephenson, Changle Chen, Alessandro Motta, Massimiliano Delferro, Jennifer P Mcinnis, Michael P Weberski, Tobin J. Marks
    Abstract:

    The synthesis, structural characterization, and ethylene Polymerization properties of two neutrally charged Ni(II) phenoxyiminato catalysts are compared and contrasted. Complex FI-SO2-Ni features a −SO2– group embedded in the ligand skeleton, whereas control FI-CH2-Ni has the −SO2– replaced by a −CH2– functionality. In comparison with FI-CH2-Ni, at 25 °C, FI-SO2-Ni is 18 times more active, produces polyethylene with 3.2 times greater MW and 1.5 times branch content, and is significantly more thermally stable. The FI-SO2-Ni-derived polymer is a hyperbranched polyethylene (148 branches 1000 C–1, MW = 3500g mol–1) versus that from FI-CH2-Ni (98 branches 1000 C–1, MW = 1100g mol–1). DFT calculations argue that the distinctive FI-SO2-Ni catalytic behavior versus that of FI-CH2-Ni is associated with nonnegligible OSO···Ni interactions involving the activated catalyst.

  • proximity and cooperativity effects in binuclear d 0 olefin Polymerization Catalysis theoretical analysis of structure and reaction mechanism
    Journal of the American Chemical Society, 2009
    Co-Authors: Alessandro Motta, Ignazio L Fragala, Tobin J. Marks
    Abstract:

    This contribution focuses on the distinctive center-to-center cooperative catalytic properties exhibited by bimetallic “constrained geometry catalysts” (CGCs), and analyzes metal−metal proximity effects on ethylene Polymerization processes mediated by (μ-CH2-3,3′){(η5-indenyl)[1-H2Si(tBuN)](ZrMe2)}2 (Zr2)-derived catalysts using density functional theory. Precatalyst geometries are first discussed, and then ion-pair formation/heterolytic dissociation processes involving the binuclear bis(borane) cocatalyst 1,4-(C6F5)2BC6F4B(C6F5)2 (BN2), are analyzed and compared with those in the parent mononuclear analogue. It is found that, on proceeding from the mononuclear to binuclear catalyst system, ion-pair dissociation energies increase due to the stronger catalyst center-counterdianion interactions. Moreover, in the binuclear case, the interaction energies are markedly sensitive to geometrical matching between the binuclear bis(borane) and the precatalyst Zr−methyl positions. Binuclear catalytic effects between...

  • proximity and cooperativity effects in binuclear d 0 olefin Polymerization Catalysis theoretical analysis of structure and reaction mechanism
    Journal of the American Chemical Society, 2009
    Co-Authors: Alessandro Motta, Ignazio L Fragala, Tobin J. Marks
    Abstract:

    This contribution focuses on the distinctive center-to-center cooperative catalytic properties exhibited by bimetallic "constrained geometry catalysts" (CGCs), and analyzes metal-metal proximity effects on ethylene Polymerization processes mediated by (mu-CH(2)-3,3'){(eta(5)-indenyl)[1-H(2)Si((t)BuN)](ZrMe(2))}(2) (Zr(2))-derived catalysts using density functional theory. Precatalyst geometries are first discussed, and then ion-pair formation/heterolytic dissociation processes involving the binuclear bis(borane) cocatalyst 1,4-(C(6)F(5))(2)BC(6)F(4)B(C(6)F(5))(2) (BN(2)), are analyzed and compared with those in the parent mononuclear analogue. It is found that, on proceeding from the mononuclear to binuclear catalyst system, ion-pair dissociation energies increase due to the stronger catalyst center-counterdianion interactions. Moreover, in the binuclear case, the interaction energies are markedly sensitive to geometrical matching between the binuclear bis(borane) and the precatalyst Zr-methyl positions. Binuclear catalytic effects between the metal centers are then explored, with the specific contribution from the proximity of the second metal center. Possible agostic interactions of alpha-alkenes pi-coordinated to one Zr center with the second Zr center of the binuclear catalyst are scrutinized for the case of 1-octene. It is argued that these agostic interactions are at least partly responsible for the unusual enchainment properties of the bimetallic catalysts. In particular, the greater polyethylene product branch densities found experimentally for the bimetallic catalysts can be correlated with an intramolecular reinsertion process, assisted by agostic interactions. Moreover, these same agostic interactions involving a chain growing at one metal site with the second metal site of the binuclear catalyst modify the environment to increase propagation/termination rate ratios, in turn favoring increased product molecular weight (M(n)). These effects are observed experimentally at closer Zr...Zr proximities in olefin Polymerizations mediated by binuclear CGC catalysts.

Charlotte K Williams - One of the best experts on this subject based on the ideXlab platform.

  • switchable Polymerization Catalysis using a tin ii catalyst and commercial monomers to toughen poly l lactide
    ACS Macro Letters, 2021
    Co-Authors: Nattawut Yuntawattana, Georgina L Gregory, Leticia Pena Carrodeguas, Charlotte K Williams
    Abstract:

    Sustainable plastics sourced without virgin petrochemicals, that are easily recyclable and with potential for degradation at end of life, are urgently needed. Here, copolymersand blends meeting these criteria are efficiently prepared using a single catalyst and existing commercial monomers l-lactide, propylene oxide, and maleic anhydride. The selective, one-reactor Polymerization applies an industry-relevant tin(II) catalyst. Tapered, miscible block polyesters are formed with alkene groups which are postfunctionalized to modulate the polymer glass transition temperature. The polymers are blended at desirable low weight fractions (2 wt %) with commercial poly(l-lactide) (PLLA), increasing toughness, and elongation at break without compromising the elastic modulus, tensile strength, or thermal properties. The selective Polymerization Catalysis, using commercial monomers and catalyst, provides a straightforward means to improve bioplastics performances.

  • Sequence Control from Mixtures: Switchable Polymerization Catalysis and Future Materials Applications.
    Journal of the American Chemical Society, 2021
    Co-Authors: Arron C Deacy, Georgina L Gregory, Gregory S Sulley, Thomas T D Chen, Charlotte K Williams
    Abstract:

    There is an ever-increasing demand for higher-performing polymeric materials counterbalanced by the need for sustainability throughout the life cycle. Copolymers comprising ester, carbonate, or ether linkages could fulfill some of this demand as their monomer-polymer chemistry is closer to equilibrium, facilitating (bio)degradation and recycling; many monomers are or could be sourced from renewables or waste. Here, an efficient and broadly applicable route to make such copolymers is discussed, a form of switchable Polymerization Catalysis which exploits a single catalyst, switched between different catalytic cycles, to prepare block sequence selective copolymers from monomer mixtures. This perspective presents the principles of this Catalysis, catalyst design criteria, the selectivity and structural copolymer characterization tools, and the properties of the resulting copolymers. Uses as thermoplastic elastomers, toughened plastics, adhesives, and self-assembled nanostructures, and for programmed degradation, among others, are discussed. The state-of-the-art research into both Catalysis and products, as well as future challenges and directions, are presented.

  • selective Polymerization Catalysis from monomer mixtures using a commercial cr salen catalyst to access aba block polyesters
    Angewandte Chemie, 2018
    Co-Authors: Tim Stoser, Charlotte K Williams
    Abstract:

    : ABA triblock polyesters are synthesized using a commercially available chromium salen catalyst, in one pot, from monomer mixtures comprising epoxide, anhydride and lactone. The Catalysis is highly selective and applies a single catalyst in two distinct pathways. It occurs first by epoxide/anhydride ring-opening coPolymerization and subsequently by lactone ring-opening Polymerization. It is used to produce various new ABA polyester polyols; these polyols can undergo post-functionalization and chain-extension reactions. The ability to use a commercial catalyst and switchable Catalysis with monomer mixtures is expected to facilitate future explorations of new classes of block polymers.

  • Multiblock Polyesters Demonstrating High Elasticity and Shape Memory Effects
    2018
    Co-Authors: Yunqing Zhu, Madalyn R. Radlauer, Deborah K. Schneiderman, Milo S. P. Shaffer, Marc A. Hillmyer, Charlotte K Williams
    Abstract:

    Polyester block polymers containing polylactide have garnered significant attention as renewable, degradable alternatives to traditional elastomers. However, the low glass transition of the PLA blocks limits the upper-use temperatures of the resulting elastomers. To improve the thermal performance, we explore a series of multiblock polyesters composed of poly­(ε-decalactone) (PDL) and poly­(cyclohexene phthalate) (PCHPE). These materials are prepared using switchable Polymerization Catalysis followed by chain extension. The strategy involves (i) alternating ring-opening coPolymerization (ROCOP) of cyclohexene oxide and phthalic anhydride, (ii) ε-decalactone ring-opening Polymerization (ROP), and (iii) diisocyanate coupling of the telechelic triblocks to increase molar mass. The resulting multiblock polyesters are amorphous, and the blocks are phase separated; glass transition temperatures are ∼−45 and 100 °C. They show thermal resistance to mass loss with Td5% ∼ 285 °C and higher upper use temperatures compared to alternative aliphatic polyesters. The nanoscale phase behavior and correlated mechanical properties are highly sensitive to the block composition. The sample containing PCHPE = 26 wt % behaves as a thermoplastic elastomer with high elongation at break (εb > 2450%), moderate tensile strength (σb = 12 MPa), and low residual strain (εr ∼ 4%). It shows elastomeric behavior from −20 to 100 °C and has a processing temperature range of ∼170 °C. At higher PCHPE content (59 wt %), the material has shape memory character with high strain fixation (250%) and recovery (96%) over multiple (25) recovery cycles. The multiblock polyesters are straightforward to prepare, and the methods presented here can be extended to produce a wide range of new materials using a other epoxides, anhydrides, and lactones. This first report on the thermal and mechanical properties highlights the significant potential for this class of polyesters as elastomers, rigid plastics, and shape memory materials

  • macrocyclic dizinc ii alkyl and alkoxide complexes reversible co2 uptake and Polymerization Catalysis testing
    Inorganic Chemistry, 2015
    Co-Authors: Charles Romain, Michael S Bennington, Charlotte K Williams, Andrew J. P. White, Sally Brooker
    Abstract:

    The synthesis of three new dizinc(II) complexes bearing a macrocyclic [2 + 2] Schiff base ligand is reported. The bis(anilido)tetraimine macrocycle reacts with diethylzinc to form a bis(ethyl)dizinc(II) complex, [LEtZn2Et2] (1). The reaction of complex 1 with isopropyl alcohol is reported, forming a bis(isopropyl alkoxide)dizinc complex, [LEtZn2(iPrO)2] (2). Furthermore, complex 1, with 2 equiv of alcohol, is applied as an initiator for racemic lactide ring-opening Polymerization. It shows moderately high activity, resulting in a pseudo-first-order rate coefficient of 9.8 × 10–3 min–1, with [LA] = 1 M and [initiator] = 5 mM at 25 °C and in a tetrahydrofuran solvent. Polymerization occurs with good control, as evidenced by the linear fit to a plot of molecular weight versus conversion, the narrow dispersities, and the limited transesterification. The same initiating system is inactive for the ring-opening coPolymerization of carbon dioxide (CO2) and cyclohexene oxide at 80 °C and 1 bar of CO2 pressure. How...

Alessandro Motta - One of the best experts on this subject based on the ideXlab platform.

  • pyridylamido bi hafnium olefin Polymerization Catalysis conformationally supported hf hf enchainment cooperativity
    ACS Catalysis, 2015
    Co-Authors: Yanshan Gao, Cristiano Zuccaccia, Alceo Macchioni, Aidan R Mouat, Alessandro Motta, Massimiliano Delferro, Tobin J. Marks
    Abstract:

    Homobimetallic Hf(IV) complexes, L2-Hf2Me5 (3) and L2-Hf2Me4 (4) (L2 = N,N′-{[naphthalene-1,4-diylbis(pyridine-6,2-diyl)]bis[(2-isopropylphenyl)methylene)]bis(2,6-diisopropylaniline}), were synthesized by reaction of the free ligand L2 with the appropriate Hf precursor and were characterized in solution (NMR) and in the solid state (X-ray diffraction). In 3, L2 acts as a dianionic tridentate ligand for one Hf metal center and as a monoanionic bidentate ligand for the other, whereas in 4, both Hf units are tricoordinated to opposite sides of L2. In the solid state, the Hf···Hf distance is significantly different in 3 vs 4 (6.16 vs 8.06 A, respectively), but in solution, the structural dynamics of the two linked metallic units in bis-activated complex 3 accesses conformers with far closer Hf···Hf distances (∼3.2 A). Once activated with Ph3C+B(C6F5)4– (B1) or PhNMe2H+B(C6F5)4– (NB), 3 exhibits pronounced bimetallic cooperative effects in ethylene homoPolymerization and ethylene +1-octene coPolymerization vs ...

  • ni ii phenoxyiminato olefin Polymerization Catalysis striking coordinative modulation of hyperbranched polymer microstructure and stability by a proximate sulfonyl group
    ACS Catalysis, 2014
    Co-Authors: Casey J Stephenson, Changle Chen, Alessandro Motta, Massimiliano Delferro, Jennifer P Mcinnis, Michael P Weberski, Tobin J. Marks
    Abstract:

    The synthesis, structural characterization, and ethylene Polymerization properties of two neutrally charged Ni(II) phenoxyiminato catalysts are compared and contrasted. Complex FI-SO2-Ni features a...

  • ni ii phenoxyiminato olefin Polymerization Catalysis striking coordinative modulation of hyperbranched polymer microstructure and stability by a proximate sulfonyl group
    ACS Catalysis, 2014
    Co-Authors: Casey J Stephenson, Changle Chen, Alessandro Motta, Massimiliano Delferro, Jennifer P Mcinnis, Michael P Weberski, Tobin J. Marks
    Abstract:

    The synthesis, structural characterization, and ethylene Polymerization properties of two neutrally charged Ni(II) phenoxyiminato catalysts are compared and contrasted. Complex FI-SO2-Ni features a −SO2– group embedded in the ligand skeleton, whereas control FI-CH2-Ni has the −SO2– replaced by a −CH2– functionality. In comparison with FI-CH2-Ni, at 25 °C, FI-SO2-Ni is 18 times more active, produces polyethylene with 3.2 times greater MW and 1.5 times branch content, and is significantly more thermally stable. The FI-SO2-Ni-derived polymer is a hyperbranched polyethylene (148 branches 1000 C–1, MW = 3500g mol–1) versus that from FI-CH2-Ni (98 branches 1000 C–1, MW = 1100g mol–1). DFT calculations argue that the distinctive FI-SO2-Ni catalytic behavior versus that of FI-CH2-Ni is associated with nonnegligible OSO···Ni interactions involving the activated catalyst.

  • proximity and cooperativity effects in binuclear d 0 olefin Polymerization Catalysis theoretical analysis of structure and reaction mechanism
    Journal of the American Chemical Society, 2009
    Co-Authors: Alessandro Motta, Ignazio L Fragala, Tobin J. Marks
    Abstract:

    This contribution focuses on the distinctive center-to-center cooperative catalytic properties exhibited by bimetallic “constrained geometry catalysts” (CGCs), and analyzes metal−metal proximity effects on ethylene Polymerization processes mediated by (μ-CH2-3,3′){(η5-indenyl)[1-H2Si(tBuN)](ZrMe2)}2 (Zr2)-derived catalysts using density functional theory. Precatalyst geometries are first discussed, and then ion-pair formation/heterolytic dissociation processes involving the binuclear bis(borane) cocatalyst 1,4-(C6F5)2BC6F4B(C6F5)2 (BN2), are analyzed and compared with those in the parent mononuclear analogue. It is found that, on proceeding from the mononuclear to binuclear catalyst system, ion-pair dissociation energies increase due to the stronger catalyst center-counterdianion interactions. Moreover, in the binuclear case, the interaction energies are markedly sensitive to geometrical matching between the binuclear bis(borane) and the precatalyst Zr−methyl positions. Binuclear catalytic effects between...

  • proximity and cooperativity effects in binuclear d 0 olefin Polymerization Catalysis theoretical analysis of structure and reaction mechanism
    Journal of the American Chemical Society, 2009
    Co-Authors: Alessandro Motta, Ignazio L Fragala, Tobin J. Marks
    Abstract:

    This contribution focuses on the distinctive center-to-center cooperative catalytic properties exhibited by bimetallic "constrained geometry catalysts" (CGCs), and analyzes metal-metal proximity effects on ethylene Polymerization processes mediated by (mu-CH(2)-3,3'){(eta(5)-indenyl)[1-H(2)Si((t)BuN)](ZrMe(2))}(2) (Zr(2))-derived catalysts using density functional theory. Precatalyst geometries are first discussed, and then ion-pair formation/heterolytic dissociation processes involving the binuclear bis(borane) cocatalyst 1,4-(C(6)F(5))(2)BC(6)F(4)B(C(6)F(5))(2) (BN(2)), are analyzed and compared with those in the parent mononuclear analogue. It is found that, on proceeding from the mononuclear to binuclear catalyst system, ion-pair dissociation energies increase due to the stronger catalyst center-counterdianion interactions. Moreover, in the binuclear case, the interaction energies are markedly sensitive to geometrical matching between the binuclear bis(borane) and the precatalyst Zr-methyl positions. Binuclear catalytic effects between the metal centers are then explored, with the specific contribution from the proximity of the second metal center. Possible agostic interactions of alpha-alkenes pi-coordinated to one Zr center with the second Zr center of the binuclear catalyst are scrutinized for the case of 1-octene. It is argued that these agostic interactions are at least partly responsible for the unusual enchainment properties of the bimetallic catalysts. In particular, the greater polyethylene product branch densities found experimentally for the bimetallic catalysts can be correlated with an intramolecular reinsertion process, assisted by agostic interactions. Moreover, these same agostic interactions involving a chain growing at one metal site with the second metal site of the binuclear catalyst modify the environment to increase propagation/termination rate ratios, in turn favoring increased product molecular weight (M(n)). These effects are observed experimentally at closer Zr...Zr proximities in olefin Polymerizations mediated by binuclear CGC catalysts.

Jun Okuda - One of the best experts on this subject based on the ideXlab platform.

  • rare earth metal complexes supported by 1 ω dithiaalkanediyl bridged bis phenolato ligands synthesis characterization and ring opening Polymerization Catalysis ofl lactide
    Dalton Transactions, 2003
    Co-Authors: Thomas P Spaniol, Jun Okuda
    Abstract:

    Monomeric rare earth metal bis(phenolato) complexes [(Ls,s)Ln{N(SiHMe2)2}(THF)] (1a–4c) were isolated from the reaction of silylamido complexes [Ln{N(SiHMe2)2}3(THF)x] (Ln = Sc, x = 1; Ln = Y, Lu, x = 2) and one equivalent of tetradentate 1,ω-dithiaalkanediyl-bridged bis(phenol)s etbmpH2, ptbmpH2, edtbpH2 and pdtbpH2 in moderate to high yields. In contrast to the unsymmetrical scandium complexes 1a and 3a, the scandium complex 2a, the yttrium complexes 1b and 4b as well as the lutetium complexes 1c–4c show Cs or C2 symmetry due to the relatively fast dissociation of THF on the NMR time scale at room temperature. The monomeric structures of the complexes 2a and 4b were confirmed by X-ray diffraction studies. The six-coordinate central metal with the tetradentate ligand, the silylamido group, and one THF, adopts a C1 symmetrical configuration with trans(O,O) or cis(O,O) orientation of the two oxygen donors of the ligand. Distorted octahedral and trigonal prismatic coordination geometries are found for 2a and 4b. Substitution reaction with 2,2,6,6-tetramethyl-3,5-heptanedione afforded the corresponding complexes 6b, 6c, 7c and 8b with dimeric structures and with trityl alcohol the alkoxide complex [(etbmp)Y(OCPh3)(THF)] (9). All new complexes efficiently initiated the ring-opening Polymerization of L-lactide in THF. High molecular weight poly(L-lactide)s with narrow molecular weight distributions (Mw/Mn 1.15–1.41) were obtained using complexes 1a–4c. Dimeric β-diketonato complexes were only active in the presence of THF or excess isopropanol.

  • complexes of titanium and zirconium containing a tridentate linked amido cyclopentadienyl ligand with a soft donor group synthesis structure and ethylene Polymerization Catalysis
    Journal of Organometallic Chemistry, 1999
    Co-Authors: Jun Okuda, Thomas P Spaniol, Thomas Eberle, Valerie Piquetfaure
    Abstract:

    Abstract Group 4 metal complexes M(η5:η1-C5R4SiMe2NCH2CH2SMe)Cl2 (R=H, M=Ti; R=Me, M=Ti, Zr) containing the thioether-functionalized linked amido–cyclopentadienyl ligand were synthesized and characterized by 1H- and 13C-NMR spectroscopy, mass spectrometry, and elemental analysis. The crystal structures of the complexes Ti(η5:η1-C5H4SiMe2NCH2CH2SMe)Cl2 and Zr(η5:η1:η1-C5Me4SiMe2NCH2CH2SMe)Cl2 were determined by single-crystal X-ray diffraction studies. The titanium complex is a conventional three-legged piano-stool molecule without an intramolecular interaction between the sulfur donor group and the titanium center, whereas the zirconium complex adopts a trigonal bipyramidal structure, with the five-membered ring and the coordinating methylthio group in the apical positions. Reaction between the titanium dibenzyl Ti(η5:η1-C5Me4ZNCH2CH2SMe)(CH2Ph)2 (Z=SiMe2, CH2SiMe2) and B(C6F5)3 in C6D5Br resulted in the clean formation of the solvent-separated ion pair [Ti(η5:η1-C5Me4ZNCH2CH2SMe)(η2-CH2Ph)]+[(PhCH2)B(C6F5)3]−. The dichloro complexes M(η5:η1-C5Me4SiMe2NCH2CH2SMe)Cl2, when activated with methylaluminoxane, catalyzed the Polymerization of ethylene with moderate activities. The phosphino-functionalized ligand C5Me4SiMe2NC6H4(PPh2)-2 was also coordinated at titanium and zirconium centers; NMR spectroscopic data inferred an intramolecular metal–phosphine interaction for these M{η5:η1-C5Me4SiMe2NC6H4(PPh2)-2}Cl2 complexes.

  • alkyl complexes of group 4 metals containing a tridentate linked amido cyclopentadienyl ligand synthesis structure and reactivity including ethylene Polymerization Catalysis
    Organometallics, 1998
    Co-Authors: Francisco Amor, Angelika Butt, Karen E Du Plooy, Thomas P Spaniol, Jun Okuda
    Abstract:

    A series of group 4 metal complexes M(η5:η1:η1-C5Me4SiMe2NCH2CH2X)R2 (M = Ti; R = Me, CH2Ph; M = Zr, Hf; R = Me, Et, nPr, nBu, CH2Ph, CH2SiMe3, Ph) containing the tridentate-linked amido−tetramethy...

M Knobel - One of the best experts on this subject based on the ideXlab platform.

  • synthesis structural and magnetic characterization of a copper ii complex of 2 6 di 1h imidazol 2 yl pyridine and its application in copper mediated Polymerization Catalysis
    Inorganica Chimica Acta, 2017
    Co-Authors: E. G. R. De ,arruda, M. A. De ,farias, Sergio Augusto Venturinelli Jannuzzi, Stella A Gonsales, Ronaldo Adriano Timm, S K Sharma, Giorgio Zoppellaro, Lauro T Kubota, M Knobel
    Abstract:

    Abstract The 2,6-di(1H-imidazol-2-yl)pyridine (H2dimpy) ligand is synthesized and suggested as an alternative ligand for copper mediated Catalysis. A Cu(II) complex was obtained with this ligand and characterized via ESI-MS, FT-IR, UV–vis and the structure was confirmed by single crystal XRD. The crystal showed the [ Cu 2 ( H 2 dimpy ) 2 ( μ - Cl ) 2 ] ( PF 6 ) 2 · 2 H 2 O dimeric complex, in which Cu(II) is in a distorted square-pyramidal geometry ( τ = 0.301 ). Ferromagnetic coupling with J = - 11.1  cm−1 was confirmed by experiment and corroborated by density functional calculations. In order to evaluate the applicability of H2dimpy in atom transfer radical Polymerization (ATRP), polystyrene was produced in DMF solution at low polydispersity (1.3) while maintaining the livingness of the polymer chain. The good performance of the H2dimpy compared to a standard ligand for ATRP (5,5′-dimethyl-2,2′-dipyridyl) indicates that it is suitable for this reaction.