A New Type of Lewis Acid–Base Bifunctional M(salphen) (M=Zn, Cu and Ni) Catalysts for CO₂ Fixation

Abstract

A new type of Lewis acid–base bifunctional M(salphen) complexes (M=ZnII, CuII, and NiII) pending two N‐methylhomo‐ piperazine groups as nucleophiles were prepared by a one‐pot method. The Zn(salphen) complexes proved to be efficient and recyclable homogeneous catalysts towards the solvent‐free synthesis of cyclic carbonates from epoxides and CO2 in the absence of a co‐catalyst. The catalysts can be easily recovered and five times reused without significant loss of activity and selectivity.

A Ni(salen)‐Based Metal–Organic Framework: Synthesis, Structure, and Catalytic Performance for CO2 Cycloaddition with Epoxides

“…In all experiments, cyclic carbonates were the sole products. As was reported in other literature, the very good yield of epichlorohydrin (entry 3, Table ) can be explained by the electron‐withdrawing substituents, which facilitate nucleophilic attack of Br – during the ring opening of epoxide. It is worthwhile to note that the yield of cyclic carbonates gradually decreased with the increase in alkyl chain length of epoxides, exhibiting size‐dependent selectivity.…”

“…Indeed, upon extending the reaction time to 24 hours, the yield of cyclic carbonates with longer alkyl chains reached 99 %. To our delight, the internal epoxide, cyclohexene oxide, which is known to poorly undergo cycloaddition with CO 2 because of the high steric hindrance, was converted into the corresponding cyclic carbonate with a moderate yield of 68 % (entry 7, Table ), further demonstrating the high catalytic performance of this MOF catalyst.…”

Catalysis of Cycloaddition of Carbon Dioxide and Epoxides Using a Bifunctional Schiff Base Iron(III) Catalyst

“…For example, Al(salen) with two intramolecular quaternary ammonium substituents and Zn(salpyr) [salpyr=N,N’‐bis(salicylidene)‐3,4‐pyridinediamine] with N‐methyl‐pyridinium [14] utilize attached quaternary amine as a source of nucleophile (Br − or I − , respectively). On the other hand, Cr(III)(salen) linked with MTBD (7‐methyl‐1,5,7‐triazabicyclo[4.4.0] dec‐5‐ene), and M(salphen) complexes (M=Zn(II), Cu(II), and Ni(II)) substituted with two N‐methylhomopiperazine groups represent a concept where the nucleophile is an amine based.…”

Zinc Imine Polyhedral Oligomeric Silsesquioxane as a Quattro‐Site Catalyst for the Synthesis of Cyclic Carbonates from Epoxides and Low‐Pressure CO2

“…Cyclic carbonates are characterized by a range of applications, for instance: monomers for polymerization, substrates in organic synthesis, green solvents, or electrolytes for lithium‐ion batteries [48, 49] . From the above reasons, a number of research groups have focused their attention on the preparation of efficient catalytic systems for cyclic carbonate synthesis including metal complexes with imine, [50–54] aminophenolate, [55, 56] porphyrin, [57, 58] or other ligands [59–62] . Also, an organocatalytic approach has actively been investigated [63–65] …”