Theoretical Studies on Bimetallic Salen Complexes Catalyzed Epoxide Hydration: Effects of Metal Centers, Substrates, and Ligands

Abstract

To provide guiding information for developing efficient and stable catalysts for epoxide hydration, we investigated the mechanism of propylene oxide (PO) to 1,2-propylene glycol (PG) using density functional theory (DFT) calculations. The mechanism was identified to follow the cooperative bimetallic mechanism in which a metal–salen complex activated H2O attacks the middle carbon atom of a metal–salen complex activated PO from the oxygen side of three-membered ring. Analyses reveal that the distortion energy correlates linearly with the barrier, and the hydrogen bonding between H2O and PO increases from reaction precursors to transition states. A nice linear relationship exists between the ratio of square root of ionic potential to the square of the distance from the metal ion spherical surface to the oxygen atom center of PO. It is demonstrated that the substrates with larger polarizability tend to have lower hydration barriers and the influence of ligands is less than that of metal centers and substrates. Modifying metal ions is the first choice for developing metal–salen catalysts, and metal ions with more formal charges and larger radius are expected to exhibit high activity. These findings shed lights on the mechanism and provide guiding information for developing efficient metal–salen catalysts for epoxide hydration.

Synthesis, Characterization, and Study of Catalytic Activity of Chiral Cu(II) and Ni(II) Salen Complexes in the α-Amino Acid C-α Alkylation Reaction

“…Chiral salen transition metal complexes have a significant role in the stereoselective synthesis being efficient chiral catalysts usable in a plethora of asymmetric transformations [ 1 , 2 , 3 , 4 ]. Their simple synthesis and the versatility in their structural modification have contributed to the current increased interest in the synthesis and characterization of new salen metal complexes [ 5 , 6 , 7 , 8 , 9 , 10 ]. From an applicative perspective, such complexes of the first-row transition metals are known for their attractive catalytic, magnetic and biological properties [ 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 ].…”

“…J = 2.6 Hz, 1H),6.88 (d, J = 2.6 Hz, 1H), 2.97 (s, 1H), 2.46 (s, 1H), 1.93 (s, 1H), 1.42 (s, 8H), 1.33 (d, J = 6.0 Hz, 2H), 1.27 (s, 9H) ppm 13. C NMR (75 MHz, Chloroform-d): δ 157.8, 129.1, 126.3, 96.3, 69.9, 35.9, 33.9, 31.5, 29.8, 29.0, 24.6 ppm.…”

The Journal of Physical Chemistry C Virtual Special Issue on “Energy and Catalysis in China”

“…CO oxidation on RuO 2 (110) surfaces, 85 Pt nanocatalysts, 86 Cu/Rh bimetallic catalysts, 87 Ag clusters, 88 and Ru/RuO 2 interfaces 89 is discussed. Theoretical studies on other important reactions are also included: the HER on the VS 2 monolayer 90 or black phosphorus, 91 the electrochemical CO 2 reduction reaction on h-BN nanosheets, 92 photocatalytic CO 2 reduction on silver nanoclusters, 93 CO 2 dissociation on Cu clusters, 94 the methanol-to-olefins (MTO) process on different zeolites, 95 the ORR on the two-dimensional NiTe monolayer, 96 the nitrogen reduction reaction on Ru-or Fe-supported Nb 2 C MXene, 97 NO reduction by CO on Cu 2 O(110) and Pd 1 / Cu 2 O(110), 98 NO oxidation on different oxides, 99 methane steam reforming on Ni, Pt, and Pd, 100 dry reforming of methane on the Ni/Mo alloy, 101 the B 2 O 3 -catalyzed oxidative dehydrogenation of propane, 102 the hydrodeoxygenation of hydroquinone on Au/TiO 2 , 103 the hydrogenation of CO 2 to methanol over Pt 4 /In 2 O 3 , 104 syngas conversion to ketene on ZnCr 2 O 4 , 105 the structural and optoelectronic properties of ZnSe 1−x Te x photocatalysts, 106 bimetallic salen-complex-catalyzed epoxide hydration, 107 Rh-catalyzed formaldehyde hydroformylation, 108 the peroxidase and oxidase-like properties of nanoceria in biosystems, 109 the formation of polarons in TiO 2 , HfO 2 , and BiVO 4 , 110,111 and interfacial charge transfer in Li− O 2 batteries. 112 This VSI reflects the recent progress in the experimental and theoretical development of chemical energy in mainland China.…”