(Imidazol-2-ylidene) → S coordination interactions and its modulation upon S-oxidation
Joy Mukhopadhyay1, Subash C Sahoo2, Prasad V Bharatam1
1Department of Medicinal Chemistry, National Institute of Pharmaceutical Education and Research (NIPER), Sector 67, S. A. S. Nagar, Punjab 160062, India. pvbharatam@niper.ac.in.
Dalton Transactions (Cambridge, England : 2003)
|October 2, 2024
Summary
N-heterocyclic carbenes (NHC) form coordination bonds with sulfur. This study shows NHC-sulfur interactions strengthen as sulfur gains oxygen atoms, confirmed through quantum chemical design and synthesis.
Area of Science:
- Coordination Chemistry
- Organosulfur Chemistry
- N-heterocyclic Carbene Chemistry
Background:
- N-heterocyclic carbene (NHC) coordination interactions are common with many elements.
- NHC-sulfur interactions are less explored but gaining interest.
- Increased positive charge on sulfur enhances NHC-sulfur interactions.
Purpose of the Study:
- To investigate the hypothesis that S-oxidation enhances NHC-sulfur coordination.
- To explore NHC → SR(+), NHC → S(O)R(+), and NHC → S(O)2R(+) complexes.
- To synthesize and characterize novel NHC-sulfur compounds.
Main Methods:
- Quantum chemical design and computational modeling.
- Synthesis of eight (imidazol-2-ylidene) → SR(+) derivatives.
- Oxidation of sulfur centers using urea-H2O2 and mCPBA.
- X-ray crystallography for structural determination.
Main Results:
- Successfully synthesized and characterized NHC-sulfur, NHC-sulfoxide, and NHC-sulfone complexes.
- Crystal structures confirmed the coordination interactions.
- Geometric, energetic, and electronic analyses demonstrated strengthening interactions.
Conclusions:
- The hypothesis is confirmed: NHC → S coordination strength increases with sulfur oxidation.
- Oxidation state of sulfur significantly influences the NHC-sulfur bond.
- This work expands the understanding of NHC coordination chemistry with sulfur.
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