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1,3-Bis(2,6-di-i-propylphenyl)imidazolium chloride
CAS: 250285-32-6
SKU: S2961
1,3-Bis(2,6-di-i-propylphenyl)imidazolium chloride | SKU: S2961
synonyms: IPr·HCl; IPr hydrochloride; 1,3-Bis(2,6-diisopropylphenyl)imidazolium chloride; 1,3-Bis(2,6-diisopropylphenyl)-1H-imidazol-3-ium chloride
1,3-Bis(2,6-di-i-propylphenyl)imidazolium chloride
IPr·HCl is the imidazolium chloride salt from which the N-heterocyclic carbene (NHC) ligand IPr is generated. The cation carries a 2,6-diisopropylphenyl group on each nitrogen of an imidazolium ring, and these bulky aryl wings shield the metal centre in the finished catalyst. The salt is a stable, free-flowing solid (C27H37ClN2, molecular weight 425.05 g/mol) that decomposes at about 278 °C, so unlike the free carbene it can be weighed and stored on the bench. Deprotonating the C2–H position with a base such as potassium tert-butoxide or an alkali-metal hexamethyldisilazide releases the carbene, either in situ or before complexation. IPr is a strong σ-donor with a large steric profile, properties that stabilise low-coordinate, electron-rich metal centres and make aryl chlorides practical substrates in cross-coupling chemistry. IPr·HCl is therefore the standard entry point for well-defined palladium, nickel, gold, copper and ruthenium NHC complexes, and it is also used directly alongside a metal source, for example with palladium acetate to form a catalyst for the carbonylative coupling of pyridyl halides with aryl boronic acids. Sarchem Labs offers IPr·HCl (SKU S2961) for catalyst development, process chemistry and academic research. Each lot ships with a Certificate of Analysis and Safety Data Sheet, and laboratory to bulk quantities can be quoted on request. The compound is classified as acutely toxic if swallowed, so please read the safety information below before ordering.
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Specifications

Melting Point278°C (dec.) (lit.)
ColorUndesignated
Formula Weight425.06
Physical FormCrystal-Powder at 20°C
Chemical Name or Material1,3-Bis(2,6-diisopropylphenyl)imidazolium chloride
Molecular Weight425.05 g/mol
SMILES String[Cl-].CC(C)c1cccc(C(C)C)c1-n2cc[n+](c2)-c3c(cccc3C(C)C)C(C)C
Assay97%
CAS Number250285-32-6
NACRESNA.22
PubChem Substance ID24880705
UNSPSC Code12352005
MDL NumberMFCD02684545
InChI1S/C27H37N2.ClH/c1-18(2)22-11-9-12-23(19(3)4)26(22)28-15-16-29(17-28)27-24(20(5)6)13-10-14-25(27)21(7)8;/h9-21H,1-8H3;1H/q+1;/p-1
InChI KeyAVJBQMXODCVJCJ-UHFFFAOYSA-M
PubChem CID2734913
Reaction SuitabilityReagent type: ligand
Quality Level200
FormSolid (crystal-powder at 20°C)
Empirical Formula (Hill Notation)C27H37ClN2

Applications

No Application Found
PEPPSI-type precatalysts: the starting material for air-stable [(IPr)PdCl2(3-chloropyridine)] and related precatalysts that are widely used in process development because they are easy to handle and activate in the reaction flask.
Gold and copper catalysis: a precursor to (IPr)AuCl and (IPr)CuCl, which catalyse alkyne hydrofunctionalisation, cycloisomerisation and borylation reactions once the halide is removed or replaced.
Nickel and ruthenium catalysis: supplies the bulky NHC ligand for nickel-catalysed cross-couplings and cycloadditions and for ruthenium olefin-metathesis catalysts.
Main-group and organometallic research: the free carbene derived from the salt stabilises reactive low-valent main-group and transition-metal fragments for structural and mechanistic studies.
Pharmaceutical and agrochemical route scouting: a standard member of ligand screening sets for C–C and C–N bond formation, where NHC ligands complement phosphines.

Product Description

What is IPr·HCl?

IPr·HCl is an organic salt made of a 1,3-bis(2,6-diisopropylphenyl)imidazolium cation and a chloride anion, with the formula C27H37ClN2 and a molecular weight of 425.05 g/mol. “IPr” is the standard abbreviation for the corresponding carbene, 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene. The acidic C2–H proton of the imidazolium ring is removed by base to form that carbene, which then binds to a metal. Sigma-Aldrich lists the 97% reference grade as a solid that melts with decomposition at 278 °C and assigns it the reagent type “ligand”.

Uses of IPr·HCl

IPr-based catalysts combine high activity with robust, well-defined structures. In palladium catalysis, the size of the ligand favours the reductive-elimination step and its strong donation speeds oxidative addition into unreactive aryl chlorides, which is why Pd–NHC systems are used for Suzuki–Miyaura couplings and C–N bond formation at low catalyst loadings. In gold catalysis, [(IPr)AuCl] activated with a silver salt is a benchmark catalyst for alkyne and allene transformations, and nickel and copper complexes of IPr appear in cross-coupling, hydrosilylation and borylation methods.

Using the preformed salt rather than the free carbene avoids handling an air- and moisture-sensitive solid: the carbene is generated only when it is needed, in the same flask as the metal precursor if desired. This convenience is why imidazolium salts such as IPr·HCl dominate the NHC ligand market.

Buying and Handling Considerations

Check the assay and the water content on the Certificate of Analysis, since imidazolium chlorides can retain traces of water or solvent that matter when the salt is deprotonated with a strong base. Keep the container tightly closed in a dry place. Sigma-Aldrich assigns the compound to storage class 6.1A (very toxic hazardous materials) with the hazard statement H300 (fatal if swallowed), so weigh it in a fume hood or glove box, avoid creating dust and follow your site’s procedures for acutely toxic solids. Because it is also very toxic to aquatic life (H410), collect all waste as hazardous waste and keep it out of drains.

Safety Information

Based on Sigma-Aldrich’s verified classification (574074).

  • Pictograms / Signal Word: GHS06 (skull and crossbones), GHS05 (corrosion), GHS09 (environment) | Danger
  • Hazard Statements: H300 (fatal if swallowed), H318 (causes serious eye damage), H335 (may cause respiratory irritation), H410 (very toxic to aquatic life with long-lasting effects)
  • Hazard Classification: Acute Tox. 2 Oral, Eye Dam. 1, STOT SE 3 (target organ: respiratory system), Aquatic Acute 1, Aquatic Chronic 1
  • Precautionary Statements: P261, P264, P273, P280, P301 + P310, P305 + P351 + P338
  • Storage Class: 6.1A – Combustible acute toxic Cat. 1 and 2 / very toxic hazardous materials | WGK: 3 | Flash Point: not applicable
  • PPE: Type N95 (US) dust mask, eyeshields, gloves

Do not eat, drink or smoke where the material is used, and wash hands thoroughly after handling.

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FAQs: 1,3-Bis(2,6-di-i-propylphenyl)imidazolium chloride

It is the precursor to the bulky N-heterocyclic carbene ligand IPr, used to make palladium, nickel, gold, copper and ruthenium catalysts for cross-coupling, olefin metathesis, alkyne activation and related transformations.

IPr is the free carbene, an air- and moisture-sensitive species. IPr·HCl is its stable imidazolium chloride salt, which releases IPr when it is deprotonated by a base.

Treat the salt with a strong, non-nucleophilic base such as potassium tert-butoxide, sodium hydride or KHMDS in an anhydrous solvent under inert gas. Many catalysts are prepared by mixing the salt, a base and a metal precursor in one flask.

The formula is C27H37ClN2, the molecular weight is 425.05 g/mol and the literature melting point is 278 °C with decomposition.

Sigma-Aldrich classifies it as fatal if swallowed (H300), causing serious eye damage (H318), a respiratory irritant (H335) and very toxic to aquatic life (H410). Handle it in a fume hood with gloves, eye protection and a dust mask.

The imidazolium salt is a stable solid that can be handled in air for weighing, whereas the free carbene is not. Keep the container tightly closed and dry, and dry the salt before use if the downstream chemistry is moisture-sensitive.

Yes. Sarchem Labs provides a Certificate of Analysis and Safety Data Sheet with every lot of SKU S2961 and quotes bulk quantities on request.