Browsing by Author "Valderrama, Mauricio"

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    Cyclometallated platinum(II) complexes containing the chiral ligand [2-(diphenyl-phosphanyl)-benzylidene]-(1-phenyl-ethyl)-amine: Synthesis and molecular structures of the compounds [PtCl(Me){kappa(2)-(R)-Ph2P(C6H4)CH=NCH(Ph)Me-P,N}] and [Pt{kappa(3)-(S)-Ph2P(C6H4)CH=NCH(C6H4)Me-P,N,C}Py]BF4
    (ELSEVIER SCIENCE SA, 2008) Ramirez, Paola; Contreras, Raul; Valderrama, Mauricio; Carmona, Daniel; Lahoz, Fernando J.; Balana, Ana I.
    Diastoreoisomeric mixtures of the complex [PtIMe3{kappa(2)-Ph2P(C6H4)CH=NCH(Ph)Me-P,N}] (Rc-1) react with AgBF4 and SMePh to give a mixture of complexes [PtMe(SMePh) {kappa(2)-Ph2P(C6H4)CH=NCH(Ph)Me-P,N}]BF4 (2) and [Pt{kappa(2)-Ph2P(C(6)H4)CH=NCH(C6H4)Me-P,N,C}(PhSMe)]BF4 (3) which subsequently render the corresponding chloride compounds [PtClMe{kappa(2)-(R)-Ph2P(C6H4)CH=NCH(Ph)Me-P,N}] (4) and [PtCl{kappa(3)-(R)-Ph2P(C6H4)CH=NCH(C6H4)Me-P,N,C}] (5), by elution with CH2Cl2 on a aluminium oxide chromatography column. Refluxing of [PtIMe3{kappa(2)-Ph2P(C6H4)CH=NC*H(Ph)Me-P,N}] (Sc-1) with AgBF4 in a 1:1, CH2Cl2:Me2CO mixture followed by the addition of SMePh, NCMe or pyridine (Py) affords the corresponding cyclometallated compounds [Pt{kappa(3)-(S)-Ph2P(C6H4)CH=NCH(C6H4)Me-P,N,C}(L)]BF4 [L = SMePh (3), NCMe (9), Py (10)]. These compounds have been characterised by analytical and spectroscopic means and by the molecular structure determination of complexes 4 and 10. (C) 2007 Elsevier B.V. All rights reserved.
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    Mono and bimetallic nickel bromide complexes bearing azolate-imine ligands: Synthesis, structural characterization and ethylene polymerization studies
    (ELSEVIER SCIENCE SA, 2009) Caris, Rodrigo; Peoples, Brian C.; Valderrama, Mauricio; Wu, Guang; Rojas, Rene
    The synthesis of N-(1-(3,5-dimethylpyrazol-1-yl)ethylidene)-2,6-diisopropylaniline (1) and N-(1-(indazol-2-yl)ethylidene)-2,6-diisopropylaniline (2) allowed access to new transition metal complexes. When reacted with dibromo(2,2'-dimethoxyethylether) nickel(II) the complexes [NiBr2{N-(1-(3,5-dimethylpyrazol-1-yl) ethylidene)-2,6-diisopropylaniline}] (3) and [Ni2Br2(mu-Br)2{N-(1-(indazol-1-yl)ethylidene)-2,6-diisopropylaniline} 2] (4) are yielded, respectively. The addition of MAO generates catalytically active species for the homopolymerization of ethylene. The polymer products were low molecular weight (3-6 K) and a monomodal molecular weight distribution, consistent with the presence of a single active site. In addition, the catalyst was found to efficiently oligomerize higher olefins to high molecular weights with narrow PDIs. (C) 2009 Elsevier B.V. All rights reserved.
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    New bis(azolylcarbonyl)pyridine chromium(III) complexes as initiators for ethylene polymerization
    (ELSEVIER SCIENCE SA, 2011) Hurtado, John; Ugarte, Javiera; Rojas, Rene; Valderrama, Mauricio; Mac Leod Carey, Desmond; Munoz Castro, Alvaro; Arratia Perez, Ramiro; Froehlich, Roland
    Reaction of 2,6-pyridinedicarbonyl dichloride with 3,5-dimethylpyrazole and 1H-indazole, respectively, yield the tridentate ligands 2,6-bis(3,5-dimethylpyrazol-1-ylcarbonyl)pyridine (1) and 2,6-bis(indazol-1-ylcarbonyl)pyridine (2). The molecular structure of the new compound (2) was determined by single-crystal X-ray diffraction. These ligands react with CrCl3(THF)(3) in THF to form neutral complexes of general formula [CrCl3{2,6-bis(azolylcarbonyl)pyridine-N,N,N}] (3, 4) which were isolated in high yield as air stable green solids and characterized by elemental analysis, magnetic moment, IR, and mass spectroscopies. Theoretical calculations predict that the thermodynamically preferred structure of the complexes is the fac configuration. After reaction with methylaluminoxane (MAO) the chromium(III) complexes are active for the polymerization of ethylene. (C) 2011 Elsevier B.V. All rights reserved.
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    Nickel pre-catalysts bearing [(N)-imidoylamidine] ligands; influence of the presence of pyridine and pentafluorophenyl groups in ligand backbone on the reactivity in ethylene polymerizations
    (2012) Peoples, Brian C.; De la Vega, Gala; Valdebenito, Carolina; Quijada, Raul; Ibanez, Andres; Valderrama, Mauricio; Rojas, Rene
    In this contribution the synthesis and polymerization activity of the nickel complexes [NiBr2{N'-(2,6-diisopropylphenyl)-N-[1-(2,6-diisopropylphenylimine)ethyl]-N-(2,3,4,5,6-pentafluorophenyl)acetamidine}] (2), [NiBr2{N'-(2,6-diisopropylphenyl)-N-[1-(2,6-diisopropylphenylimine)ethyl]-N-(2,3,4,5,6-pentafluorophenylimine) ethylacetamidine}] (2a) and [NiBr2 {N-(2,6-diisopropylphenyl)-N-[1-(2,6-diisopropylphenylimine)]-N-(pyridin-4-yl)acetamidine}] (3)are reported. The variation of the phenyl substituents on the beta amine was found to influence the polymerization activity of the complexes. The electron withdrawing/donating capacity of the substituted ring was found to be correlated with the polymerization activity, with the pentafluoro substituted ring increasing the polymerization activity and the pyridine ring decreasing the activity. The ligands and complexes were characterized using standard techniques and the polymer properties analyzed. (C) 2011 Elsevier B. V. All rights reserved.
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    PALLADIUM COMPLEX BEARING 3,5-BIS(BENZOTRIAZOL-1-YLMETHYL) TOLUENE LIGAND CATALYZES OXIDATIVE AMINATION OF ALLYL BUTYL ETHER
    (2013) Hurtado, John; Rojas, Rene S.; Perez, Edwin G.; Valderrama, Mauricio
    The reaction of 3,5-bis(bromomethyl)toluene with benzotriazole yields the bidentate ligand 3,5-bis(benzotriazol-1-ylmethyl)toluene (1). This ligand reacts with [PdCl2(cod)] (cod = 1,5-cyclooctadiene) to give the complex [PdCl2{3,5-bis(benzotriazol-1-ylmethyl)tolyl}] (2). These compounds were characterized by elemental analyses, mass spectra, and FTIR and NMR (H-1, C-13) spectroscopies. The palladium(II) complex 2 shows high activity as catalyst for oxidative amination, involving allyl butyl ether and phthalimide as substrates and PhICl2 as a stoichiometric oxidant.
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    Synthesis and coordination properties of chiral bidentate P,O-donor ligands
    (SOC CHILENA QUIMICA, 2006) Diaz, Oscar; Contreras, Raul; Valderrama, Mauricio
    Reaction of the chiral compound (S)-(+)-BrCH2CHMeCH2OH with Ph2PK in the presence of lithium diisopropylamide (LDA) and BH3/THF yields the monophosphine (S)-Ph2P(BH3)CH2CHMeCH2OH(1). The reaction of 1 with ClOSO2Me/Et2N or NaH/Mel gives rise to the formation of the general compound (S)-Ph2P(BH3)CH2CHMeCH2OR [R = SO2Me (2), Me (5)], which by treatrent with pyrrolidine affords (S)-Ph2PCH2CHMeCH2OR [R = SOMe (4), Me (6)). The monophophines 4, 6 and (S)-PPh2CH2CHMeCH2OH react with [{Cp*IrCl(mu-Cl)(2)] to give the neutral compounds [Cp*IrCl2(PPh2CH2CHMeCH2OR-P)], where only the compound with R - H (7) was fully characterized. Complex 7 reacts with AgBF4 yielding the cationic complex [Cp*IrCl(PPh2CH2CHMeCH2OH-PO)]BF4 (8) in which the ligand acts in its bidentate form. Similar synthetic results were obtained using [jCp*IrI(mu-I)(2)] as starting complex.
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    Synthesis and structure of dicarbonyldichloro{2-(diphenylphosphineoxide)pyridine}ruthenium(II)
    (SOC CHILENA QUIMICA, 2008) Diaz, Oscar; Medina, Soledad; Valderrama, Mauricio; Lahoz, Fernando J.; Martin, M. Luisa
    Reaction of the dinuclear complex [{Ru(CO)(3)Cl-2}(2)] with the ligand 2-(diphenylphosphineoxide)pyridine (PyPOPh2) in ethanol solution gave the neutral mononuclear complex [Ru(k(2)-PyPOPh2-N,O)(CO)(2)Cl-2]. The complex was characterized by elemental analysis, IR and RMN spectroscopy, and its molecular structure was determined by single-crystal X-ray diffraction.
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    Tris(pyrazolyl)methane-chromium(III) complexes as highly active catalysts for ethylene polymerization
    (ELSEVIER SCIENCE BV, 2006) Garcia Rozco, Ivan; Quijada, Raul; Vera, Karen; Valderrama, Mauricio
    Reaction of complex CrCl3 (THF)(3) with the tris(pyrazolyl)methane ligands, HC(Pz)(3), HC(3,5-Me(2)Pz)(3) and their substituted derivatives RC(Pz)(3) (R = Me, CH2OH, CH2OSO2Me) in THF lead to the formation of neutral complexes of the types [RC(PZ)(3)CrCl3] and [RC(3,5-Me(2)PZ)(3)CrCl3]. After reaction with methylalumoxane (MAO) these complexes are active in the polymerization of ethylene. The substituent on the methane central carbon atom of the ligand has some influence in polymerization behavior. This compounds present higher activities than similar chromium complexes, in the ethylene polymerization reaction. (c) 2006 Elsevier B.V. All rights reserved.