N‐Formylation of Amines with CO₂ and H₂ by Using NHC–Iridium Coordination Assemblies as Solid Molecular Catalysts

Abstract

One of the NHC-iridium coordination assemblies containing 1,5-cyclooctadiene (COD) and iodide ion has been demonstrated as robust, efficient, recyclable solid molecular catalyst for N-formylation of diverse primary and secondary amines with CO and H under mild reaction conditions. Remarkably, in the case of N,N-dimethylformamide production, even at 0.1 mol % catalyst loading under solvent-free conditions, the solid catalyst can be readily recovered by simply filtration and reused more than 10 runs without noticeable loss of activity.

Highly Efficient and Selective N‐Formylation of Amines with CO2 and H2 Catalyzed by Porous Organometallic Polymers

“…As shown in Figure 3 a, in the presence of 0.002 mol % catalyst loading under a CO 2 /H 2 partial pressure of 40/40 atm at 120 °C for 24 hours, POMP‐NHC‐Ir 2 a – h exhibited much higher catalytic activity than their homogeneous precursor bis‐NHC‐Ir complex 1 . 1 H NMR and GC analyses of the reaction mixtures revealed that water was the only byproduct, in consistency with the previous reports [9, 11a] . For comparison, other known viable homogeneous catalysts 4 – 6 for the N‐formylation were also tested under the optimized reaction conditions, and much lower yields were attained (Figure 3 a).…”

“…Other commercially available catalysts, like Vaska's catalyst 6 , resulted in trace amount of DMF. In the case of our previously reported linear nonporous self‐supported NHC‐Ir coordination polymer 3 a with a BET surface area of 8 m 2 g −1 , [11a] only 36 % yield was achieved at such low catalyst loading. All these outcomes indicated that the preserved chemical environment around the iridium center, large specific surface area, hierarchical porous structure of POMP‐NHC‐Ir were all necessary to achieve satisfactory outcomes in the challenging catalytic N‐formylation reaction with CO 2 and H 2 .…”

“…To solve the above problems, by combining the advantages of homogenous and heterogenous catalytic systems, we have previously reported a series of linear N‐heterocyclic carbene iridium (NHC‐Ir) coordination polymers [11] via the self‐supporting strategy [12] . Owing to the isolated effect, the possible clusterization of NHC‐Ir molecules are prohibited, [13] and the resulting linear self‐supported catalysts exhibited excellent catalytic activity (up to 99 % yield, Figure 1 b), wide substrate scope and good reusability (up to 10 times) in the N‐formylation reaction [11a] . Unfortunately, only a moderate TON (730) was achieved, probably due to the restriction of the extremely low specific surface area and the nonporous feature within the linear catalyst.…”

From ‘Gift’ to gift: producing organic solvents from CO2

“…Later, Tu and co-workers explored a series of NHC-Ir coordination assemblies as solid molecular catalysts for N-formylation of diverse amines. 63 Moderate yield of DMF was attained, even at 0.1 mol% catalyst loading, and the solid catalyst could be reused more than 10 runs.…”

Homogeneous (De)hydrogenative Catalysis for Circular Chemistry – Using Waste as a Resource

“…Moreover, recycling of the catalyst was also demonstrated for up to 12 cycles for the production of N, N‐dimethylformamide without significant loss of activity. Tu has recently reported a solid molecular catalyst based on the iridium‐NHC coordination assembly ( Ir‐3 , Figure 6) for the N‐formylation of a variety of amines using CO 2 and H 2 [90] . A solid molecular catalyst allowed easy recovery of the catalyst by a simple filtration process that could be used more than 10 times without loss of activity for the production of DMF in solvent‐free conditions.…”