Single-Crystal Cobalt Phosphide Nanorods as a High-Performance Catalyst for Reductive Amination of Carbonyl Compounds

Abstract

The development of metal phosphide catalysts for organic synthesis is still in its early stages. Herein, we report the successful synthesis of single-crystal cobalt phosphide nanorods (Co 2 P NRs) containing coordinatively unsaturated Co–Co active sites, which serve as a new class of air-stable, highly active, and reusable heterogeneous catalysts for the reductive amination of carbonyl compounds. The Co 2 P NR catalyst showed high activity for the transformation of a broad range of carbonyl compounds to their corresponding primary amines using an aqueous ammonia solution or ammonium acetate as a green amination reagent at 1 bar of H 2 pressure; these conditions are far milder than previously reported. The air stability and high activity of the Co 2 P NRs is noteworthy, as conventional Co catalysts are air-sensitive (pyrophorous) and show no activity for this transformation under mild conditions. P-alloying is therefore of considerable importance for nanoengineering air-stable and highly active non-noble-metal catalysts for organic synthesis.

Electrooxidative tricyclic 6–7–6 fused-system domino assembly to allocolchicines by a removable radical strategy

“…Subsequently, 3a was converted to the desulfonylation product enone 5 following a perylene-catalyzed photodesulfonylation procedure. 22 Then, catalytic hydrogenation of alkene 5 led to the formation of dibenzocycloheptanone 6, which provided the allocolchicinoid 9 after cobalt phosphide nanorods (Co 2 P NRs) catalyzed reductive amination 23 followed by acetylation. Notably, though the reductive amination showed poor selectivity between amine 8 and alcohol 7 (7 was also formed in about 50% yield), 7 could be converted into ketone 6 by simple oxidation.…”

Advances in the Catalytic Reductive Amination of Furfural to Furfural Amine: The Momentous Role of Active Metal Sites

“…In line with this, the alloying of non‐metal, such as phosphorous, has a positive role in stabilizing low valent metals like Co, thus enhancing hydrogenation capability by increasing the d‐electron density of the metal [82] . Recently, air‐stable single‐crystal cobalt phosphide nanorods have been developed for the reductive amination of benzaldehyde as a model substrate, with unsaturated Co−Co species as active sites (confirmed by FT‐EXAFS) [83] . Further, the activity of Co 2 P nanorods has been expanded to a broad range of carbonyl compounds (yielding 70–99 % corresponding amine), including FUR, producing 90 % FUA at 100 °C, 5 bar H 2 in aqueous ammonia.…”

“…[82] Recently, air-stable singlecrystal cobalt phosphide nanorods have been developed for the reductive amination of benzaldehyde as a model substrate, with unsaturated CoÀ Co species as active sites (confirmed by FT-EXAFS). [83] Further, the activity of Co 2 P nanorods has been expanded to a broad range of carbonyl compounds (yielding 70-99 % corresponding amine), including FUR, producing 90 % FUA at 100 °C, 5 bar H 2 in aqueous ammonia. The XANES spectrum of cobalt phosphide nanorods indicates the presence of Co species in a metallic state.…”

Phosphorus-Alloying as a Powerful Method for Designing Highly Active and Durable Metal Nanoparticle Catalysts for the Deoxygenation of Sulfoxides: Ligand and Ensemble Effects of Phosphorus

“… 5 − 8 However, despite their unique properties the use of metal phosphide catalysts in organic syntheses has rarely been investigated. 9 − 13 Our group recently reported the unique catalytic properties exhibited by nonprecious metal phosphide (Ni 2 P and Co 2 P) NPs in selective liquid-phase molecular transformations, e.g., the transformation of biomass-derived molecules; 14 − 18 the hydrogenation of nitriles, carbonyls, nitroarenes, and sulfoxides; 19 − 22 the reductive amination of carbonyls; 23 and the alkylation of oxindoles. 24 These studies revealed the potential of nonprecious metal phosphide NPs to serve as a novel class of highly efficient heterogeneous catalysts for versatile liquid-phase reactions, outperforming conventional single nonprecious metal NPs.…”