86010-97-1Relevant academic research and scientific papers
Synthesis, characterization, and catalase activity of a water-soluble diMnIII complex of a sulphonato-substituted schiff base ligand: An efficient catalyst for H2O2 disproportionation
Palopoli, Claudia,Bruzzo, Natalia,Hureau, Christelle,Ladeira, Sonia,Murgida, Daniel,Signorella, Sandra
experimental part, p. 8973 - 8983 (2011/10/18)
A new diMnIII complex, Na[Mn2(3-Me-5-SO 3-salpentO)(μ-MeO)(μ-AcO)(H2O)]?4H 2O (1), where salpentOH = 1,5-bis(salicylidenamino) pentan-3-ol, was synthesized and structurally characterized. The complex possesses a bis(μ-alkoxo)(μ-acetato) triply bridged diMnIII core, the structure of which is retained upon dissolution. Complex 1 is highly efficient to disproportionate H2O2 in an aqueous solution of pH ≥ 8.5 or in DMF, with only a slight decrease of activity. Electrospray ionization mass spectrometry, EPR, and UV-vis spectroscopy used to monitor the H 2O2 disproportionation in buffered basic medium, suggest that the major active form of the catalyst during cycling occurs in the Mn III2 oxidation state and that the starting complex retains the dinuclearity and composition during catalysis, with the acetate that moves from bridging to terminal ligand. UV-vis and Raman spectroscopy of H 2O2 + 1 + Bu4NOH mixtures in DMF suggest that the catalytic cycle involves MnIII2/MnIV 2 oxidation levels. At pH 10.6 in an Et3N/Et 3NH+ buffer, complex 1 catalyzes dismutation of H 2O2 with saturation kinetics on the substrate, first order dependence on the catalyst, and kcat/KM = 16(1) ×102 s-1 M-1. During catalysis, the exogenous base contributes to retain the integrity of the bis(μ-alkoxo) doubly bridged diMn core and favors the formation of the catalyst-peroxide adduct (low value of KM), rendering 1 a highly efficient catalyst for H2O2 disproportionation.
Zinc(II) homogeneous and heterogeneous species and their application for the ring-opening polymerisation of rac-lactide
Jones, Matthew D.,Davidson, Matthew G.,Keir, Callum G.,Hughes, Laura M.,Mahon, Mary F.,Apperley, David C.
experimental part, p. 635 - 642 (2009/05/06)
Schiff base ligands (L1H-L8H) have been prepared and complexed to Zn II centres. All eight complexes have been characterised by single-crystal X-ray diffraction methods, multinuclear NMR spectroscopy and elemental analysis. It was shown that fo
A family of zirconium complexes having two phenoxy - imine chelate ligands for olefin polymerization
Matsui,Mitani,Saito,Tohi,Makio,Matsukawa,Takagi,Tsuru,Nitabaru,Nakano,Tanaka,Kashiwa,Fujita
, p. 6847 - 6856 (2007/10/03)
A zirconium complex having two phenoxy - imine chelate ligands, bis[N-(3-tert-butylsalicylidene)-anilinato]zirconium(IV)dichloride (1), was found to display a very high ethylene polymerization activity of 550 kg of polymer/mmol of cat·h with a viscosity average molecular weight, (Mv) value of 0.9 × 104 at 25 °C at atmospheric pressure using methylalumoxane (MAO) as a cocatalyst. This activity is 1 order of magnitude larger than that exhibited by Cp2ZrCl2 under the same polymerization conditions. The use of Ph3CB(C6F5)4/i-Bu3Al in place of MAO as a cocatalyst resulted in extremely high molecular weight polyethylene, Mv 505 × 104, with an activity of 11 kg of polymer/mmol of cat·h at 50 °C. This Mv value is one of the highest values displayed by homogeneous olefin polymerization catalysts. Complex 1, using Ph3CB(C6F5)4/i-BU3Al as a cocatalyst, provided a high molecular weight ethylene-propylene copolymer, Mv 109 × 104, with 8 kg of polymer/mmol of cat·h activity at a propylene content of 20.7 mol %. X-ray analysis revealed that complex 1 adopts a distorted octahedral coordination structure around the zirconium metal and that two oxygen atoms are situated in trans position while two nitrogen atoms and two chlorine atoms are situated in cis position. DFT calculations suggest that the active species derived from complex 1 possesses two available cis-located sites for efficient ethylene polymerization. Changing the tert-butyl group in the phenoxy benzene ring enhanced the polymerization activity. Bis[N-(3-cumyl-5-methylsalicylidene)cyclohexylaminato]zirconium(IV)dichloride (7) with MAO displayed an ethylene polymerization activity of 4315 kg of polymer/mmol of cat·h at 25 °C at atmospheric pressure. This activity corresponds to a catalyst turnover frequency (TOF) value of 42 900/s· atm. This TOF value is one of the largest not only for olefin polymerization but also for any known catalytic reaction. Ligands with additional steric congestion near the polymerization reaction center gave increased Mv values. The maximum Mv value, 220 × 104 using MAO, was obtained with bis[N-(3,5-dicumylsalicylidene)-2′-isopropylanilinato]zirconium (IV)dichloride (15). Thus, polyethylenes ranging from low to exceptionally high molecular weights can be obtained from these zirconium complexes by changing the ligand structure and the choice of cocatalyst.
