DSpace Angular :: Browsing by Author "Daniliuc, Constantin G."

Browsing by Author "Daniliuc, Constantin G."

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Bulky and Electron-Deficient α-Iminocarboxamidato-Nickel(II) Complexes: A Study of the Steric and Electronic Effects on Ethylene Activation
(2021) Skarjan, Leon; Villegas-Escobar, Nery; Correa, Sebastian A.; Daniliuc, Constantin G.; Matute, Ricardo A.; Rojas, Rene S.
Two alpha-iminocarboxamidato-nickel(II) complexes containing ligands with several CF3 groups were synthesized and characterized by NMR spectroscopy, elemental analysis, and density functional theory (DFT) calculations. Surprisingly, the prepared complexes were inactive toward ethylene oligo/polymerization reactions upon activation attempts with common lewis acid co-catalysts such as B(C6F5)(3) and BF3. Quantum chemistry calculations were employed to reveal that adduct formation is thermodynamically favored for small Lewis acids such as BF3 due to the sterically demanding ligand environment of the complex, confirming the experimental findings. DFT results associate the lack of polymerization activity with a highly unfavorable steric environment, undesirable London dispersion interactions between the ligands, and a strong electrostatic stabilization caused by the employed ligands. Our findings should help future researchers to identify necessary electronic and steric requirements for the compounds to generate active Ni(II) catalysts for ethylene oligo/polymerization activated by suitable boron Lewis acids.
Cyclic Carbonates from CO2 and Epoxides Catalyzed by Tetra- and Pentacoordinate Amidinate Aluminum Complexes
(2019) Ríos Yepes, Yersica; Quintero Ramírez, Celso Noé; Osorio Meléndez, Danay Katherine; Daniliuc, Constantin G.; Martínez, Javier; Rojas Guerrero, René
Heteroleptic Cu(i) complexes bearing methoxycarbonyl-imidoylindazole and POP ligands-an experimental and theoretical study of their photophysical properties
(2018) González Pavez, Iván Alonso; Henríquez Toro, Marco Antonio; Cortés Arriagada, Diego; Natali, Mirco; Daniliuc, Constantin G.; Dreyse, Paulina A.; Maze Ríos, Jerónimo; Rojas Guerrero, René; Salas Sánchez, Cristián Osvaldo; Cabrera Caballero, Alan Raúl
Mono- and Dinuclear Asymmetric Aluminum Guanidinates for the Catalytic CO₂ Fixation into Cyclic Carbonates
(2021) Rios Yepes, Yersica; Mesias-Salazar, Angela; Becerra, Alexandra; Daniliuc, Constantin G.; Ramos, Alberto; Fernandez-Galan, Rafael; Rodriguez-Dieguez, Antonio; Antinolo, Antonio; Carrillo-Hermosilla, Fernando; Rojas, Rene S.
A set of trisubstituted guanidine ligands L1H2-L4H2 with general formula (PrHN)(2)CNR (R = Ph (L1H2), R = 2,4,6-Me3C6H2(L2H2), R = p-BrC6H4(L3H2), R = (C5H4)Fe(C5H5), Fc (L4H2)) was employed to synthesize a family of mono- and dinuclear asymmetric methyl aluminum guanidinato compounds ((L2H)AlMe2 (1), (L4H)AlMe2 (2), (L-1)Al2Me4 (3), (L-2)Al2Me4 (4), (L-3)Al2Me4 (5), (L-4)Al2Me4 (6), (L1H)(2)AlMe (7), (L2H)(2)AlMe (8), and (L4H)(2)AlMe (9)) that were characterized by NMR spectroscopy (1-9) and single-crystal X-ray diffraction (4 and 8). These compounds were tested as catalysts for the fixation of carbon dioxide with epoxides to give cyclic carbonates, using tetrabutylammonium iodide (TBAI) as cocatalyst. The reactions were performed under solvent-free conditions at 70 degrees C and 1 bar CO2 pressure. Complexes 1-9 were more active than their respective free guanidines under the same experimental conditions for the synthesis of styrene carbonate (11a). The dinuclear complex 6 was the most efficient and active catalyst for the synthesis of several monosubstituted carbonates (11a-1) with excellent conversions and selectivities. Furthermore, the formation of some disubstituted cyclic carbonates (13a-c) using this dinuclear aluminum catalyst was also studied.
Neutral and cationic methallyl nickel complexes in alkene activation: a combined DFT, ESI-MS and chemometric approach
(2021) Trofymchuk, Oleksandra S.; Ortega, Daniela E.; Cortes-Arriagada, Diego; Pereira, Alfredo; Daniliuc, Constantin G.; Klitzke, Clecio F.; Santos, Leonardo S.; Rojas, Rene S.
Herein, we report a comparative study of ethylene activation and 1-hexene isomerization carried out with isomeric neutral and cationic methallyl nickel complexes L1Ni(eta(3)-C3H5) and [L1Ni(eta(3)-C3H5)][B(Ar-F)(4)] in the presence of borane co-catalysts. To understand the reactivity of the nickel complexes with NacNac ligands, we used chemometric methods to classify different catalysts reported to date. The mechanism of the interaction of [L1Ni(eta(3)-C3H5)][B(Ar-F)(4)]/B(C6F5)(3) with 1-hexene was studied by ESI-MS which allowed the detection of cationic species formed in situ. Moreover, there is a very small difference in reactivities from combination of nickel complexes and borane co-catalysts used for alkene isomerization, while the reactivity with ethylene of both systems is very different; [L1Ni(eta(3)-C3H5)][B(Ar-F)(4)]/B(C6F5)(3) produces butene, while L1Ni(eta(3)-C3H5)/B(C6F5)(3) forms polyethylene. Furthermore, DFT studies revealed that the origin of the catalytic activity in the cationic and neutral methallyl nickel complexes co-activated by B(C6F5)(3) is mainly from direct steric effects of the ligand-nickel center where the conformation of the chelate ring is affected by the catalyst symmetry. This work demonstrates how the cationic or neutral nature of the same system affects its catalytic and structural properties.
New air stable cationic methallyl ni complexes bearing imidoyl-indazole carboxylate ligand : Synthesis, characterization and their reactivity towards ethylene
(2016) Cabrera Caballero, Alan Raúl; Martinez, Ivan; Daniliuc, Constantin G.; Galland, Griselda B.; Salas Sánchez, Cristián Osvaldo; Rojas Guerrero, René
New imidoyl-indazole platinum (II) complexes as potential anticancer agents: Synthesis, evaluation of cytotoxicity, cell death and experimentaltheoretical DNA interaction studies
(2017) Cabrera Caballero, Alan Raúl; Espinosa Bustos, Christian Marcelo; Faundez, Mario; Meléndez Rojel, Jaime Gumercindo; Jaque Olmedo, Pablo César; Daniliuc, Constantin G.; Aguirre Ducler, Adam Jesús; Rojas Guerrero, René; Salas Sánchez, Cristián Osvaldo
Synthesis and structures of N-arylcyano-β-diketiminate zinc complexes and adducts and their application in ring-opening polymerization of L-lactide
(2015) Trofymchuk, Oleksandra S.; Daniliuc, Constantin G.; Kehr, Gerald; Erker, Gerhard; Rojas, Rene S.
Zinc amide complexes ZnL1N( SiMe3) 2, ZnL2N( SiMe3) 2 ( 1 and 2), their tris( pentafluorophenyl) borane adducts ZnL1N( SiMe3) 2$ B( C6F5) 3 ( 3), ZnL2N( SiMe3) 2$ 2B( C6F5) 3 ( 4), pentafluorophenyl zinc complex ZnL1C6F5 ( 5) and its adduct ZnL1C6F5$ B( C6F5) ( 6) supported by N- arylcyano- b- diketiminate ligands, as well as bis- ligated Zn( L2) 2 ( 7) were synthesized and characterized by NMR, IR, elemental analysis and X- ray diffraction. Zinc crystal structures of 1, 4, and 7 showed mononuclear complexes, while 2 and 5 were dimmers. ROP of L- lactide with zinc complexes and their B( C6F5) 3 adducts leads to generation of poly( L- LA) with high molecular weight and relatively narrow molecular weight distribution. The monomer conversion reached completion in 40 min only for zinc amide complex 1, while for other compounds it was necessary to use at least 5 hours to achieve significant polymerization yields. Coordination of the B( C6F5) 3 molecule close to the metal center blocks L- lactide insertion and thus decreases the activity of respective adducts in comparison with borane- free zinc complexes.
Toward a Neutral Single-Component Amidinate Iodide Aluminum Catalyst for the CO2 Fixation into Cyclic Carbonates
(2021) Saltarini, Sebastián; Villegas, Nery Andrés; Martínez, Javier; Daniliuc, Constantin G.; Matute, Ricardo A.; Gade, Lutz H.; Rojas Guerrero, René
Toward a Neutral Single-Component Amidinate Iodide Aluminum Catalyst for the CO₂ Fixation into Cyclic Carbonates
(2021) Saltarini, Sebastian; Villegas-Escobar, Nery; Martinez, Javier; Daniliuc, Constantin G.; Matute, Ricardo A.; Gade, Lutz H.; Rojas, Rene S.
A new iodide aluminum complex ({AlI(kappa(4)-naphbam)}, 3) supported by a tetradentate amidinate ligand derived from a naphthalene-1,8-bisamidine precursor (naphbamH, 1) was obtained in quantitative yield via reaction of the corresponding methyl aluminum complex ({AlMe(kappa(4)-naphbam)}, 2) with 1 equiv of I-2 in CH2Cl2 at room temperature. Complexes 2 and 3 were tested and found to be active as catalysts for the cyclic carbonate formation from epoxides at 80 degrees C and 1 bar of CO2 pressure. A first series of experiments were carried out with 1.5 mol % of the alkyl complex 2 and 1.5 mol % of tetrabutylammonium iodide (TBAI) as a cocatalyst; subsequently, the reactions were carried out with 1.5 mol % of iodide complex 3 as a single-component catalyst. Compound 3 is one of the first examples of a nonzwitterionic halide single-component aluminum catalyst producing cyclic carbonates. The full catalytic cycle with characterization of all minima and transition states was characterized by quantum chemistry calculations (QCCs) using density functional theory. QCCs on the reaction mechanism support a reaction pathway based on the exchange of the iodine contained in the catalyst by 1 equiv of epoxide, with subsequent attack of I- to the epoxide moiety producing the ring opening of the epoxide. QCCs triggered new insights for the design of more active halide catalysts in future explorations of the field.

Browsing by Author "Daniliuc, Constantin G."

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