Heterogeneous Rhodium Single-Atom-Site Catalyst Enables Chemoselective Carbene N.pptx

Heterogeneous Rhodium Single-Atom-Site Catalyst Enables Chemoselective Carbene N

1. Heterogeneous Rhodium Single-Atom-Site Catalyst Enables Chemoselective Carbene N − H Bond Insertion Name – KGS Madushan Student Number – SC/2019/11067 Level – 2 Semester - 2

2. CONTENT Introduction Objectives Preparation of SACs Characterization of Rh-SA Chemical bonding & Structure Mechanistic Insights Conclusion References

3. Introduction This research focuses on developing a new rhodium single-atom-site catalyst (Rh-SA) to improve the selectivity and efficiency of carbene insertion into N−H bonds Traditional methods struggle with selectivity due to the high reactivity of metal carbene intermediates To overcome this struggle ,synthesis of Rh-SA with R h atom surrounded by three nitrogen atoms and one phosphorus atom in a carbon support

4. OBJECTIVES The objective of this experiment is to develop a novel heterogeneous rhodium single-atom-site catalyst (Rh-SA) designed to enable chemoselective carbene N−H bond insertion reactions. Achieve high chemoselectivity Enhance catalytic efficiency Understand mechanistic insights

5. PREPARATION OF CATALYST Preparation of ZIF-8 Coating with poly(cyclotriphosphazene-co-4,4-diaminodiphenyl ether) to form ZIF-8@PZM Carbonization to create nitrogen and phosphorus co-doped carbon support (NP-C ) Dispersion in rhodium(III) chloride solution and annealing to obtain Rh-SA

6. CONT… Figure 1.

7. Characterization of Rh-SA TEM & HAADF-STEM : Polyhedral shape, homogeneous distribution of Rh atoms EDS Mapping : Uniform distribution of Rh, P, N, and C XRD : Presence of carbon nanostructures without metallic Rh nanoparticles

8. CONT… Figure 2. Atomic structural analysis of Rh-SA was performed by XAFS spectroscopy. (a) Rh K-edge XANES profiles of Rh-SA and its reference samples. (b) Rh K-edge EXAFS Fourier transforms of the Rh-SA and its reference samples. The Fourier transforms are not corrected for the phase shift. (c–e) Rh K-edge wavelet transform EXAFS contour plots of Rh-SA (c), Rh foil (d), and [Rh(N 2 H 4 ) 3 ]Cl 3  (e). (f, g) Rh K-edge EXAFS fitting analysis of Rh-SA in R space (f) and  k  space (g).

9. Mechanistic Insights Figure 3. Formation of the Metal Carbene Intermediate : Coordination of the Amine Substrate : Formation of the Transition State ( TS) : Completion of N-H Bond Insertion : Release of the Product and Catalyst Regeneration :

10. Figure 4. Initial State (IS) : Ground state of reactants Activation Barrier ( TS0) Intermediate State (IM1) : Transition State (TS2 ) Final State (FS) :

11. The research successfully developed a heterogeneous rhodium single-atom site (Rh-SA) catalyst, coordinated with three nitrogen atoms and one phosphorus atom . The Rh-SA catalyst exhibited efficient catalytic performance in carbene N-H insertion reactions, achieving high yields with excellent site selectivity . Density Functional Theory (DFT) studies provided - The presence of phosphorus atoms lowered the activation energy and facilitated proton transfer. The catalyst demonstrated high chemoselectivity for N-H insertion over other possible reactions, such as O-H insertion, due to the favorable transition state stabilization . CONCLUSION

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