Self-Adaptive Dirhodium Complexes in a Metal–Organic Framework for Synthesis of N–H Aziridines

Abstract

Conformational dynamics of active sites in enzymes enable great control over the catalytic process. Herein, we constructed a metal–organic framework with conformationally dynamic active sites (Rh2-ZIF-8). The active sites in Rh2-ZIF-8 were composed of the imidazolate-bridged bimetallic center with a catalytic dirhodium moiety and structural zinc site. Even though the coordination sphere of the dirhodium species was saturated with two circularly arranged esp groups and two axial 2-MeIm ligands, it could still effectively catalyze the direct synthesis of N–H aziridines from olefins with high activity. We found that such a self-adaptive catalytic process was based on the dynamic breakage and reformation of the rhodium–zinc imidazolate bridges. Interestingly, the in situ generated dirhodium site with a unique Rh2(esp)2(2-MeIm)1 configuration was able to exhibit obviously enhanced selectivity compared to homogeneous catalyst Rh2(esp)2. Furthermore, the surrounding zinc imidazolate groups could effectively protect the dirhodium moieties from harsh environments, and this ultimately endowed it with high stability.

Self-Supported Chiral Dirhodium Organic Frameworks Enables Efficient Asymmetric Cyclopropanation

“…It can be clearly noted that the adsorption property of Rh species in Rh 2 -MOCP-2 accorded with that of Rh 2 (S-Br-NTTL) 4 , which is located around 650 nm. However, Rh 2 -MOCP-1 showed different positions, which located around 600 nm compared to the band of Rh 2 (S-Br-NTTL) 4 and Rh 2 -MOCP-2. This observation suggested that the chemical environment of Rh species in Rh 2 -MOCP-1 was varied from that in Rh 2 -MOCP-2.…”

“…23−34 For example, Davies et al 24,25,35,36 reported an efficient and universal approach to immobilize a variety of chiral and achiral dirhodium catalysts cross-linked via axial binding pyridine and rhodium, such as Rh 2 (R-BNP) 4 , Rh 2 (S-PTTL) 4 , Rh 2 (S-DOSP) 4 , and Rh 2 (Oct) 4 . Jones et al 23,27,34 immobilized chiral dirhodium catalysts including Rh 2 (S-DOSP) 4 and Rh 2 (Sp-Br/Ph-TPCP) 4 on silica particles by exchanging one of the bridging ligands in a multiple-step synthesis. Very recently, Buntkowsky et al 28 designed several chiral dirhodium coordination polymers via ligand exchange employing chiral dicarboxylic acids and Rh 2 (TFA) 4 .…”

“…Dirhodium complexes are bimetallic compounds with one Rh–Rh bond and four bridging ligands at equatorial positions, displaying a unique paddle-wheel structure. − By virtue of the distinct structure and high stability, they exhibited versatile and powerful catalytic properties for a diverse array of carbine transformations of diazocarbony compounds, including cyclopropanation, C–H activation, olefins aziridination, and ylide formation. − The variety of reactions has made dirhodium complexes extremely attractive in the syntheses of important organic compounds as active pharmaceutical ingredients. − In this context, spiro -cyclopropyloxindoles constitute a unique motif of heterocycles with potential applications as potent HIV inhibitor, antitumor agent, and useful building blocks, which can be synthesized by cyclopropanation of diazooxindoles with alkenes employing dirhodium, ruthenium, mercury, and gold catalysts. − Compared to ruthenium, mercury, and gold catalysts, the dirhodium catalysts are more reactive toward alkyl-substituted alkene substrates in the cyclopropanation reaction. − However, the unsatisfactory catalyst recyclability and reusability of homogeneous dirhodium catalysts are the primary restricting factors for their practical application in industrial processes.…”

X-H Bond Insertion Promoted by Heterogeneous Dirhodium Metal–Organic Cage with Alkynes as Safe Carbene Precursors

“…To address these issues, an efficient solution is to immobilize homogeneous dirhodium catalysts into/onto heterogeneous support materials. A series of materials have been applied as the host, such as mesoporous silica, crystalline nanocellulose, coordination polymers, metal–organic frameworks (MOFs), and metal–organic cages (MOCs) [ 12 , 13 , 14 , 15 ] Porous materials based on MOCs have received much attention by acting not only as heterogeneous catalysts but also as building blocks of infinite MOFs [ 16 , 17 , 18 , 19 , 20 , 21 , 22 ]. Herein, we employed a metal–organic cage, as we previously reported [ 14 ], to heterogenize dirhodium catalysts by the self-assembly of Rh 2 (OAc) 4 with ditopic carboxylic ligands.…”

De Novo Design of Near‐Infrared Fluorescent Agents Activated by Peroxynitrite and Glutathione‐Responsive Imaging for Diabetic Liver Disease

“…In recent years, with the rapid development of molecular imaging technology, optical probes have attracted much attention relying on the advantages of high sensitivity, non‐invasive speed analysis, and high spatial resolution, and have become a potent tool for real‐time monitoring and imaging of diabetes liver disease. [ 6–14 ] Especially, due to the ability of the near‐infrared (NIR) fluorescence imaging window to detect the light emission of fluorescent dyes in the range of 650 to 900 nm, the spontaneous fluorescence of biological tissues in this range is greatly reduced, and light scattering is reduced. [ 15–25 ] Therefore, the development of near‐infrared fluorescence probes can achieve deeper non‐invasive in vivo imaging and higher spatial resolution.…”