- Schiff base manganese compound, preparation method thereof and application thereof
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The present invention provides a Schiff base manganese compound, a preparation method thereof and an application thereof. The Schiff base manganese compound has a structure of a formula I. The provided Schiff base manganese compound has a NNOO tridentate coordination ability to form a metal active center binding site to obtain a tetracoordinate Schiff base manganese catalyst. The Schiff base manganese compound is used to catalyze a ring-opening polymerization of lactide and caprolactone; the Schiff base manganese catalyst has very high activity for the ring-opening polymerization of the lactide and caprolactone, can also realize the polymerization of the monomers at room temperature, at the same time has a certain selectivity to the racemic lactide and can slightly improve the regularity of the microscopic chain structure of the polymerization product. Under the action of the catalyst, a monomer conversion rate of polylactic acid can reach 89-96%; the stereoregularity Pm of the obtained polylactic acid can reach 0.43-0.60; and a monomer conversion rate of polycaprolactone can reach 90%-95%.
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Paragraph 0086; 0087; 0088; 0089
(2019/01/07)
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- Encapsulation of SALEN- and SALHD-Mn(III) complexes in an Al-pillared clay for bicarbonate-assisted catalytic epoxidation of cyclohexene
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[Mn(3,5-dtSALEN)Cl] (I) and [Mn(3,5-dtSALHD)Cl] (II) complexes (3,5-dtSALEN = N,N′-bis(3,5-di-tert-butylsalicylaldehyde)ethylenediamine; 3,5-dtSALHD = N′N-bis-(3,5-di-tert-butylsalicylaldehyde)-1,2-cyclohexanediamine) were successfully encapsulated within
- Garcia, Ana M.,Moreno, Viviana,Delgado, Sonia X.,Ramírez, Alfonso E.,Vargas, Luis A.,Vicente, Miguel á.,Gil, Antonio,Galeano, Luis A.
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- Modulation of the catalytic activity of manganese(III) salen complexes in the epoxidation of styrene: Influence of the oxygen source
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Several achiral Mn(III) salen complexes with different groups in the diimine bridge and in the aldehyde fragment were synthesised and their catalytic activity in the epoxidation of styrene was studied at room temperature, using two oxygen sources, NaOCl or PhIO, and in two solvents, CH3CN and CH2Cl2. These manganese(III) salen complexes present high chemoselectivities as homogeneous catalysts in the epoxidation of styrene, using either iodosylbenzene or sodium hypochlorite as oxygen sources. In general, when iodosylbenzene is used as oxidant higher styrene epoxide yields and lower yields of by-products, other than benzaldehyde, are obtained than with aqueous sodium hypochlorite solutions. It was possible to tune the catalytic activities of [Mn(salen)X] complexes by introduction of substituents in the diimine bridge and in the aldehyde fragment. The presence of bulky substituents in the diimine bridge always increases the catalytic activity of these complexes, regardless of the oxidant, an indication of steric tuning. However, the electronic tuning of the catalytic activity by introducing substituents in the 5 and 3 positions of the aldehyde fragment has different effects depending on the oxygen source. For the one-phase system resulting from the use of PhIO, electron withdrawing groups increase (electron donating groups decrease) the catalytic activity of the complexes, which probably results from destabilisation (stabilisation) of [O=Mn(v)(salen)X], the identified active species making them more (less) reactive. However, when NaOCl is used, the observed behaviour is the opposite: electron donating groups make the complexes better catalysts. The apparent similarity between the solubility of the complexes in the organic solvent and their catalytic activity seems to suggest that solubility must play a key role in their activity.
- Silva, Ana Rosa,Freire, Cristina,De Castro, Baltazar
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p. 253 - 260
(2007/10/03)
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