1,3-Bis(1-adamantyl)imidazol-2-ylidene

This landmark compound is the first isolated and fully characterized stable N-heterocyclic carbene (NHC) in history — the revolutionary “Arduengo’s carbene” first reported in 1991. It represents a breakthrough in carbene chemistry, proving that singlet carbenes could be isolated as stable, bottle-able, crystalline solids under appropriate conditions.

Key Features & Properties

• Exceptional thermal stability — stable crystalline solid with melting point ~240–241 °C (without decomposition in inert atmosphere)
• Highly nucleophilic and strongly σ-donating carbene center (¹³C NMR carbene signal typically ~220–230 ppm)
• Very bulky adamantyl (1-adamantyl) substituents on both nitrogen atoms provide outstanding steric protection, effectively preventing dimerization (Wanzlick equilibrium) and greatly enhancing kinetic stability
• White to off-white crystalline powder (when handled under inert atmosphere)
• Highly air- and moisture-sensitive — must be stored and handled under dry inert gas (N₂ or Ar); reacts rapidly with oxygen and protic substances

Prime Applications

• Gold standard precursor for preparing extremely bulky NHC-metal complexes, especially of:
  • Late transition metals (Ru, Au, Cu, Pd, Pt, Ir, Rh…)
  • Widely used in second-generation Grubbs-type olefin metathesis catalysts (when hydrogenated to the saturated analog)
  • Highly active gold(I) catalysts for alkyne activation, cycloisomerizations, and selective transformations
• Benchmark ligand for studying structure-activity relationships in NHC catalysis due to its combination of extreme bulk and strong donor properties
• Fundamental research tool in organometallic chemistry, carbene reactivity studies, and ligand design

Storage & Handling Recommendation: Store under inert atmosphere at 2–8 °C. Use only in a glovebox or using Schlenk techniques. Avoid exposure to air/moisture — the compound is typically supplied under argon.

Experience the original classic of modern carbene chemistry — the molecule that opened the door to the now ubiquitous world of stable N-heterocyclic carbene ligands!