C-H bond chlorination and bromination using water soluble nickel(II) guanidine complexes
Jaipriya Khatri1, Vasanthapandiyan Mari1, Aniruddha Sarkar2
1Department of Chemistry, School of Natural Sciences, Shiv Nadar Institution of Eminence Deemed to be University, Delhi NCR, Gautam Buddha Nagar, Dadri, UP-201314, India. basabbijayi@gmail.com.
Dalton Transactions (Cambridge, England : 2003)
|December 5, 2024
Summary
Nickel(II)-guanidine complexes effectively catalyzed hydrocarbon chlorination and bromination in water. This study achieved high yields and explored the reaction mechanism using advanced spectroscopy and calculations.
Area of Science:
- Organometallic Chemistry
- Catalysis
- Green Chemistry
Background:
- C-H bond functionalization is crucial for synthesizing complex organic molecules.
- Developing efficient and environmentally friendly catalytic systems for halogenation remains a significant challenge.
- Nickel complexes offer potential as cost-effective catalysts for organic transformations.
Purpose of the Study:
- To develop water-soluble nickel(II)-guanidine complexes for catalyzing C-H chlorination and bromination reactions.
- To investigate the catalytic activity and selectivity of these complexes under mild conditions.
- To elucidate the reaction mechanism using spectroscopic and computational methods.
Main Methods:
- Synthesis of water-soluble nickel(II)-guanidine-based complexes.
- Catalytic C-H chlorination of various hydrocarbons using NaOCl in a biphasic water-chloroform system.
- Catalytic C-H bromination of hydrocarbons via in situ generation of NaOBr.
- Characterization of proposed Ni(III) intermediates using Electron Paramagnetic Resonance (EPR) spectroscopy.
- Mechanistic studies employing Density Functional Theory (DFT) calculations.
Main Results:
- Successful catalysis of C-H chlorination for multiple hydrocarbons, with high turnover numbers (e.g., ~680 for cyclohexane).
- Efficient C-H bromination of cyclohexane, n-hexane, and toluene was achieved.
- Formation of Ni(III) species was evidenced by EPR spectroscopy.
- DFT calculations supported the proposed chlorination mechanism.
Conclusions:
- Water-soluble nickel(II)-guanidine complexes are effective catalysts for C-H halogenation reactions in aqueous media.
- The catalytic system operates under mild, room-temperature conditions with high efficiency.
- The study provides mechanistic insights into nickel-catalyzed C-H functionalization.
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