Subtopic Deep Dive
N-Heterocyclic Carbene Olefin Metathesis Catalysts
Research Guide
What is N-Heterocyclic Carbene Olefin Metathesis Catalysts?
N-Heterocyclic carbene olefin metathesis catalysts are ruthenium-based complexes ligated with NHC ligands designed for olefin metathesis reactions including cross-metathesis, ring-closing metathesis, and ring-opening polymerization.
These catalysts enhance activity, stability, and selectivity through NHC ligand modifications. Key developments include second-generation ruthenium alkylidene complexes (Trnka et al., 2003, 538 citations) and chelated ruthenium catalysts for Z-selective metathesis (Endo and Grubbs, 2011, 318 citations). Over 10 major papers from 2003-2017 detail synthesis and performance metrics.
Why It Matters
NHC-Ru catalysts enable efficient synthesis of complex carbon frameworks in pharmaceuticals and materials via precise olefin metathesis. Trnka et al. (2003) demonstrated superior activity of NHC-coordinated ruthenium alkylidenes over phosphine analogs in ring-closing metathesis. Endo and Grubbs (2011) achieved high Z-selectivity, impacting natural product synthesis. Nolan et al. (2003) quantified stereoelectronic effects of saturated vs. unsaturated NHCs, guiding ligand design for industrial applications.
Key Research Challenges
Z-Selectivity in Cross-Metathesis
Achieving high Z-selectivity remains difficult due to thermodynamic preference for E-alkenes. Endo and Grubbs (2011) introduced chelating NHC ligands to address this, enabling Z-selective reactions. Further tuning is needed for challenging substrates.
Catalyst Stability Under Air
Many NHC-Ru catalysts deactivate in ambient conditions, limiting practicality. Clavier and Nolan (2007) compared indenylidene precatalysts, showing NHC variants with improved air stability. Enhanced robustness is required for large-scale synthesis.
Ligand Steric Optimization
Balancing steric bulk of NHCs affects initiation rates and selectivity. Hillier et al. (2003) used calorimetry and DFT to reveal minimal energy differences between saturated and unsaturated NHCs. Precise tuning is essential for diverse olefins.
Essential Papers
Hydrosilylation reaction of olefins: recent advances and perspectives
Yumiko Nakajima, Shigeru Shimada · 2015 · RSC Advances · 640 citations
This review focuses on the recent development of efficient, selective, and cheaper hydrosilylation catalyst systems appearing in the last decade.
Activating catalysts with mechanical force
Alessio Piermattei, S. Karthikeyan, Rint P. Sijbesma · 2009 · Nature Chemistry · 574 citations
Synthesis and Activity of Ruthenium Alkylidene Complexes Coordinated with Phosphine and N-Heterocyclic Carbene Ligands
Tina M. Trnka, John P. Morgan, Melanie S. Sanford et al. · 2003 · Journal of the American Chemical Society · 538 citations
This paper reports the synthesis and characterization of a variety of ruthenium complexes coordinated with phosphine and N-heterocyclic carbene (NHC) ligands. These complexes include several alkyli...
A Combined Experimental and Theoretical Study Examining the Binding of <i>N</i>-Heterocyclic Carbenes (NHC) to the Cp*RuCl (Cp* = η<sup>5</sup>-C<sub>5</sub>Me<sub>5</sub>) Moiety: Insight into Stereoelectronic Differences between Unsaturated and Saturated NHC Ligands
Anna C. Hillier, William Sommer, B. Yong et al. · 2003 · Organometallics · 450 citations
Combined solution calorimetric and quantum mechanics studies of reactions involving saturated and unsaturated N-heterocyclic carbene (NHC) ligands show that the difference in their relative bond di...
Application of 1,2,3-triazolylidenes as versatile NHC-type ligands: synthesis, properties, and application in catalysis and beyond
Kate F. Donnelly, Ana Petronilho, Martin Albrecht · 2012 · Chemical Communications · 371 citations
Triazolylidenes have rapidly emerged as a powerful subclass of N-heterocyclic carbene ligands for transition metals. They are readily available through regioselective [2 + 3] cycloaddition of alkyn...
Chelated Ruthenium Catalysts for <i>Z</i>-Selective Olefin Metathesis
Koji Endo, Robert H. Grubbs · 2011 · Journal of the American Chemical Society · 318 citations
We report the development of ruthenium-based metathesis catalysts with chelating N-heterocyclic carbene (NHC) ligands that catalyze highly Z-selective olefin metathesis. A very simple and convenien...
NHC–Ru complexes—Friendly catalytic tools for manifold chemical transformations
Valerian Drăguţan, Ileana Drăguţan, Lionel Delaude et al. · 2006 · Coordination Chemistry Reviews · 276 citations
Reading Guide
Foundational Papers
Start with Trnka et al. (2003, 538 citations) for core NHC-Ru alkylidene synthesis and activity benchmarks, then Hillier et al. (2003, 450 citations) for stereoelectronic insights guiding ligand choice.
Recent Advances
Study Endo and Grubbs (2011, 318 citations) for Z-selective chelated catalysts and Donnelly et al. (2012, 371 citations) for triazolylidene applications in metathesis.
Core Methods
Key techniques include NHC ligand synthesis via deprotonation, Ru coordination to form alkylidenes (Bantreil and Nolan, 2010), calorimetric binding studies (Hillier et al., 2003), and kinetic assays for selectivity (Clavier and Nolan, 2007).
How PapersFlow Helps You Research N-Heterocyclic Carbene Olefin Metathesis Catalysts
Discover & Search
Research Agent uses searchPapers and citationGraph to map Grubbs' influence, revealing Trnka et al. (2003, 538 citations) as a hub connected to Endo and Grubbs (2011). exaSearch uncovers triazolylidene variants from Donnelly et al. (2012), while findSimilarPapers expands to Nolan's indenylidene studies (Clavier and Nolan, 2007).
Analyze & Verify
Analysis Agent applies readPaperContent to extract synthesis protocols from Bantreil and Nolan (2010), then verifyResponse with CoVe checks stereoelectronic claims against Hillier et al. (2003). runPythonAnalysis plots activity data from Trnka et al. (2003) using pandas for turnover number comparisons, with GRADE scoring evidence strength on Z-selectivity metrics.
Synthesize & Write
Synthesis Agent detects gaps in Z-selective catalysts post-Endo and Grubbs (2011), flagging needs for air-stable variants. Writing Agent uses latexEditText and latexSyncCitations to draft reaction schemes citing 5+ papers, latexCompile for PDF output, and exportMermaid for catalyst cycle diagrams.
Use Cases
"Compare turnover frequencies of NHC vs phosphine Ru metathesis catalysts from Grubbs papers"
Research Agent → searchPapers('Grubbs NHC ruthenium metathesis') → Analysis Agent → readPaperContent(Trnka 2003) + runPythonAnalysis(pandas plot TOF data) → researcher gets matplotlib graph with statistical verification.
"Draft LaTeX review section on chelated NHC-Ru Z-selective catalysts"
Synthesis Agent → gap detection(Endo 2011) → Writing Agent → latexGenerateFigure(olefin metathesis cycle) + latexSyncCitations(5 papers) + latexCompile → researcher gets compiled PDF with diagrams and bibliography.
"Find GitHub repos with code for NHC-Ru catalyst modeling"
Research Agent → citationGraph(Trnka 2003) → Code Discovery → paperExtractUrls → paperFindGithubRepo → githubRepoInspect(DFT scripts) → researcher gets verified code links with README summaries.
Automated Workflows
Deep Research workflow scans 50+ NHC metathesis papers via searchPapers, structures reports on ligand effects with GRADE grading from Trnka et al. (2003). DeepScan's 7-step chain verifies Z-selectivity data from Endo and Grubbs (2011) using CoVe checkpoints. Theorizer generates hypotheses on triazolylidene improvements based on Donnelly et al. (2012).
Frequently Asked Questions
What defines NHC olefin metathesis catalysts?
Ruthenium alkylidene complexes with NHC ligands, as synthesized in Trnka et al. (2003), outperform phosphine analogs in activity and stability for ring-closing and cross-metathesis.
What are key synthesis methods?
Protocols involve coordinating NHCs to Ru precursors, detailed in Bantreil and Nolan (2010). Chelated variants use simple procedures per Endo and Grubbs (2011).
What are the most cited papers?
Trnka et al. (2003, 538 citations) on Ru alkylidenes; Hillier et al. (2003, 450 citations) on NHC binding; Endo and Grubbs (2011, 318 citations) on Z-selective catalysts.
What open problems exist?
Air-stable catalysts for unhindered olefins and higher Z-selectivity in polymerization, building on Clavier and Nolan (2007) indenylidene studies.
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