Aluminium salabza complexes for fixation of CO₂ to organic carbonates

Abstract

A highly stable and easy to synthesize aluminium complex bearing a flexible N2O2-donor salabza ligand (N,N'-bis(salicylene)-2-aminobenzylamine) in combination with tetrabutylammonium bromide forms an active binary catalytic system for the cycloaddition of CO2 to epoxides (TOFs 120-3434 h(-1)) under mild conditions (10 bar, 80 °C) and low catalyst loadings (0.05-0.2 mol%). Kinetic experiments have shown that the cycloaddition of CO2 to styrene oxide catalyzed by 1/TBAB is first order in 1, TBAB, CO2 and epoxide. A reaction mechanism is proposed based on these observations. Fe(iii) and Co(iii) related complexes are less active catalysts for this reaction.

Kinetics and mechanistic investigation of epoxide/CO2 cycloaddition by a synergistic catalytic effect of pyrrolidinopyridinium iodide and zinc halides

“…4 (a)). These results suggest the involvement of one PPI molecule in the reaction mechanism [74] . Similarly, the second series of experiments were performed using PPI in combination with ZnI 2 at a fixed concentration of PPI (76 mM) and varying the concentration of ZnI 2 over the range of 38-152 mM.…”

Triarylborane-Catalyzed Formation of Cyclic Organic Carbonates and Polycarbonates

“…Several catalysts have been described where related reactions are zero-order in CO 2 for its coupling with epoxides, i.e., independent of CO 2 pressure, ,,,, but these are typically for the formation of polycarbonate and not for the formation of the cyclic product. In examples where reaction order has been determined, it is normally first-order in CO 2 pressure for cyclic carbonate formation. ,− Therefore, an inverse order is extraordinary, so we explored the reactivity of BPh 3 under atmospheric CO 2 pressure (1.00 atm = 1.01 bar). Due to the low boiling point of propylene oxide (bp = 34 °C), we switched substrate and performed a reaction under 1 atm of CO 2 at 100 °C using glycidyl chloride (epichlorohydrin, bp = 118 °C) overnight, and >99% conversion was achieved for this reaction (TON > 3960, Table , entry 18).…”

Recent progress in the catalytic transformation of carbon dioxide into biosourced organic carbonates

“…Masdeu-Bultó et al prepared NN′O-and N 2 O 2 -type Schiffbase ligands that were used for the complexation of earthabundant metals such as zinc, 286 and aluminum, respectively (complexes 17 and 18, Table 7). 287 These complexes were found to be active Lewis acidic catalysts for the cycloaddition of CO 2 to terminal epoxides, but their application for the carbonation of iEFA1 required harsh reaction conditions (100°C, 100 bar of CO 2 ) to afford only moderate yields of iCFA1 (entries 1 and 2). Under these conditions, catalyst 18/TBAB proved to be much faster with reaction times as short as 30 min.…”

“…Under these conditions, catalyst 18/TBAB proved to be much faster with reaction times as short as 30 min. 287 Aminotriphenolates (TPA) complexes, extensively studied by the group of Kleij, 206,[288][289][290][291] are a different class of highly efficient and strongly Lewis acidic metal complexes for the cycloaddition of CO 2 to internal epoxides. In particular, TPA complexes derived from aluminum (1 R , Table 3) and vanadium (19, Table 7) are highly chemo-and stereoselective Lewis acids for the carbonation of iEFA1 under comparatively mild conditions (75-80°C, 10 bar of CO 2 ) in the presence of TBAB, obtaining cis-iCFA1 (entries 3 and 4), with the V-based binary catalyst 19/TBAB only providing moderate conversion.…”