308359-86-6Relevant academic research and scientific papers
Highly active and cis-1,4 selective polymerization of 1,3-butadiene catalyzed by cobalt(II) complexes bearing α-diimine ligands
Jia, Xiangyu,Liu, Heng,Hu, Yanming,Dai, Quanquan,Bi, Jifu,Bai, Chenxi,Zhang, Xuequan
, p. 1560 - 1569 (2013/10/01)
A series of cobalt(II) complexes bearing α-diimine ligands were synthesized and characterized by elemental and spectroscopic analysis. These complexes had the general formulas [ArN=C(Me)-(Me)C=NAr]CoCl2 (Ar = C6H5, 3a; 4-M
Synthesis and molecular and electronic structures of reduced bis(imino)pyridine cobalt dinitrogen complexes: Ligand versus metal reduction
Bowman, Amanda C.,Milsmann, Carsten,Atienza, Crisita Carmen Hojilla,Lobkovsky, Emil,Wieghardt, Karl,Chirik, Paul J.
, p. 1676 - 1684 (2010/04/02)
Sodium amalgam reduction of the aryl-substituted bis(imino)pyridine cobalt dihalide complexes (ArPDI)CoCl2 and (iPrBPDI) CoCl2 (ArPDI ) 2,6-(2,6-R2-C6H 3N=CMe)2C5H3N (R ) iPr, Et, Me); iPrBPDI ) 2,6-(2,6-iPr2-C 6H3N=CPh)2C5H3N) in the presence of an N2 atmosphere furnished the corresponding neutral cobalt dinitrogen complexes (ArPDI)CoN2 and ( iPrBPDI)CoN2. Magnetic measurements on these compounds establish doublet ground states. Two examples, (iPrPDI)CoN 2 and (iPrBPDI)CoN2, were characterized by X-ray diffraction and exhibit metrical parameters consistent with one-electron chelate reduction and a Co(I) oxidation state. Accordingly, the toluene solution EPR spectrum of (iPrPDI)CoN2 at 23 °C exhibits an isotropic signal with a g value of 2.003 and hyperfine coupling constant of 8 x 10-4 cm-1 to the I = 7/2 59Co center, suggesting a principally bis(imino)pyridine-based SOMO. Additional one-electron reduction of (iPrPDI)CoN2 was accomplished by treatment with Na[C10H8] in THF and yielded the cobalt dinitrogen anion [(iPrPDI)CoN2]-. DFT calculations on the series of cationic, neutral, and anionic bis(imino)pyridine cobalt dinitrogen compounds establish Co(I) centers in each case and a chelate-centered reduction in each of the sequential one-electron reduction steps. Frequency calculations successfully reproduce the experimentally determined N≡N infrared stretching frequencies and validate the computational methods. The electronic structures of the reduced cobalt dinitrogen complexes are evaluated in the broader context of bis(imino)pyridine base metal chemistry and the influence of the metal d electron configuration on the preference for closed-shell versus triplet diradical dianions.
Metal versus ligand alkylation in the reactivity of the (bis-iminopyridinato)Fe catalyst
Scott, Jennifer,Gambarotta, Sandro,Korobkov, Ilia,Budzelaar, Peter H. M.
, p. 13019 - 13029 (2007/10/03)
The alkylation of the Brookhart-Gibson {2,6-[2,6-(i-Pr)2PhN= C(CH3)]2(C5H3N)} FeCl2 precatalyst with 2 equiv of LiCH2Si(CH3)3 led to the isolation of several catalytically very active products depending on the reaction conditions. The expected dialkylated species {2,6-[2,6-(i-Pr) 2PhN=C(CH3)]2}(C5H 3N)Fe(CH2-SiMe3)2 (2) was indeed the major component of the reaction mixture. However, other species in which alkylation occurred at the pyridine ring ortho position, {2,6-[2,6-(i-Pr) 2PhN=C(CH3)]2-2-CH2SiMe 3}-(C5H3N)Fe(CH2SiMe3) (1), and at the imine C atom, {2-[2,6-(i-Pr)2PhN=C(CH 3)]-6-[2,6-(i-Pr)2PhNC(CH3)-(CH2 SiMe3)](C5H3N)}Fe(CH2SiMe 3) (3), have also been isolated and fully characterized. In addition, deprotonation of the methyl-imino functions and formation of a new divalent Fe catalyst {[2,6-[2,6-(i-Pr)2PhN-C=(CH2)]2(C 5H3N)}Fe(μ-Cl)Li(THF)3 (4) also occurred depending on the reaction conditions. In turn, the formation of 4 might trigger the reductive coupling of two units through the methyl-carbon wings. This process resulted in the one-electron reduction of the metal center, affording a dinuclear Fe(I) alkyl catalyst {[{[2,6-(i-Pr)2C6H 5]N=C(CH3)}(C5H3N){[2,6-(i-Pr) 2C6H5]N=CCH2}Fe(CH 2SiMe3)]}2 (5). Different from other metal derivatives, complex 5 could not be prepared from the monodeprotonated version of the ligand. Its reaction with a mixture of FeCl2 and RLi afforded instead [{2,6-[2,6-(i-Pr)2PhN-C=(CH2)]2(C 5H3N)}FeCH2Si(CH3) 3]-[Li(THF)4] (6) which is also catalytically active. All of these high-spin species have been shown to have high catalytic activity for olefin polymerization, producing polymers of two distinct natures, depending on the formal oxidation state of the metal center.
Chelate bis(imino)pyridine cobalt complexes: Synthesis, reduction, and evidence for the generation of ethene polymerization catalysts by Li+ cation activation
Kleigrewe, Nina,Steffen, Winfried,Bloemker, Tobias,Kehr, Gerald,Froehlich, Roland,Wibbeling, Birgit,Erker, Gerhard,Wasilke, Julia-Christina,Wu, Guang,Bazan, Guillermo C.
, p. 13955 - 13968 (2007/10/03)
Treatment of the bis(iminobenzyl)pyridine chelate Schiff-base ligand 8 (ligPh) with FeCl2 or CoCl2 yielded the corresponding (ligPh)MCl2 complexes 9 (Fe) and 10 (Co). The reaction of 10 with methyllithium or "butadiene-magnesium" resulted in reduction to give the corresponding (ligPh)Co(I)Cl product 11. Similarly, the bis(aryliminoethyl)pyridine ligand (ligMe) was reacted with CoCl2 to yield (ligMe)CoCl2 (12). Reduction to (ligMe)CoCl (13) was effected by treatment with "butadiene-magnesium". Complex 13 reacted with Li[B(C 6F5)4] in toluene followed by treatment with pyridine to yield [(ligMe)Co+-pyridine] (15). The reaction of the Co(II) complexes 10 or 12 with ca. 3 molar equiv of methyllithium gave the cobalt(I) complexes 16 and 17, respectively. Treatment of the (lig Me)CoCH3 (17) with Li[B(C6F5) 4] gave a low activity ethene polymerization catalyst. Likewise, complex 16 produced polyethylene (activity = 33 g(PE) mmol(cat)-1 h-1 bar-1 at room temperature) upon treatment with a stoichiometric amount of Li[B(C6F5)4]. A third ligand (ligOMe) was synthesized featuring methoxy groups in the ligand backbone (22). Coordination to FeCl2 and CoCl2 yielded the desired compounds 23 and 24. Reaction with MeLi gave (lig OMe)CoMe (25/26). Treatment of 25/26 with excess B(C 6F5)3 gave the η6-arene cation complex 27, where one Co-N linkage was cleaved. Activation of 25/26 with Li[B(C6F5)4] again gave a catalytically active species.
Iron and cobalt ethylene polymerization catalysts bearing 2,6- bis(imino)pyridyl ligands: Synthesis, structures, and polymerization studies
Britovsek, George J. P.,Bruce, Michael,Gibson, Vernon C.,Kimberley, Brian S.,Maddox, Peter J.,Mastroianni, Sergio,McTavish, Stuart J.,Redshaw, Carl,Solan, Gregory A.,Str?mberg, Staffan,White, Andrew J. P.,Williams, David J.
, p. 8728 - 8740 (2007/10/03)
The synthesis, characterization, and ethylene polymerization behavior of a series of iron and cobalt halide complexes, LMX(n) (M = Fe, X = Cl, n = 2, 3, X = Br, n = 2; M = Co, X = Cl, n = 2), bearing chelating 2,6- bis(imino)pyridyl ligands L [L = 2,6-(Ar
Highly active iron and cobalt catalysts for the polymerization of ethylene [18]
Small,Brookhart,Bennett
, p. 4049 - 4050 (2008/10/08)
Using the previously examined Ni(II) and Pd(II) α-diimine catalysts as a guide, new iron(II) and cobalt(II) catalysts based on tridentate pyridine bis-mine ligands were prepared. The resulting catalysts are robust and extremely active for polymerization of ethylene to linear, high-density polyethylene.
Novel olefin polymerization catalysts based on iron and cobalt
Britovsek, George J.P.,Gibson, Vernon C.,Kimberley, Brian S.,Maddox, Peter J.,McTavish, Stuart J.,Solan, Gregory A.,White, Andrew J.P.,Williams, David J.
, p. 849 - 850 (2007/10/03)
A new family of olefin polymerization catalysts, derived from iron and cobalt complexes bearing 2,6-bis(imino)pyridyl ligands, is described.
