1-Butyl-3-methylimidazolium Hexafluorophosphate (BMIM PF₆) (CAS 174501-64-5) — Complete Guide to Properties and Applications

What Is 1-Butyl-3-methylimidazolium Hexafluorophosphate (BMIM PF₆)?

1-Butyl-3-methylimidazolium Hexafluorophosphate (BMIM PF₆) (CAS 174501-64-5) is a hydrophobic ionic liquid with the molecular formula C₈H₁₅F₆N₂P and molecular weight 284.18 g/mol. ^[001]

The IUPAC systematic name is 1-butyl-3-methylimidazol-3-ium hexafluorophosphate. ^[001]

It appears as a colorless to pale yellow viscous liquid, melting at 6.5 °C (glass transition: −80 °C). ^[002]

Physical and Chemical Properties

How It Works

BMIM PF₆ is an ionic liquid composed of the 1-butyl-3-methylimidazolium cation and the hexafluorophosphate anion. The asymmetry of the BMIM cation (butyl vs methyl substituents) prevents efficient crystal packing, resulting in a low melting point (6.5 °C) despite the ionic nature. The PF₆⁻ anion is weakly coordinating and hydrophobic, giving the ionic liquid its immiscibility with water. This hydrophobicity is the key property enabling biphasic catalysis — organic products partition out of the IL phase while ionic catalysts remain dissolved. The imidazolium ring provides aromatic stabilization and the C2 proton is weakly acidic (pKa ~21–23), enabling hydrogen-bond donor interactions with substrates and catalysts. ^{[004] [005]}

Key Applications

1. Biphasic Catalysis & Catalyst Recycling

BMIM PF₆ is the most extensively studied hydrophobic ionic liquid for biphasic catalysis. Its water immiscibility allows retention of transition metal catalysts (Rh, Pd, Ru) in the ionic liquid phase while organic products are separated by decantation. The catalyst/IL phase can be reused 5–15 times without significant activity loss in Heck, Suzuki-Miyaura, and hydrogenation reactions. This enables continuous catalyst recycling, reducing waste and precious metal consumption. ^[004]

2. Liquid-Liquid Extraction

BMIM PF₆ efficiently extracts aromatic hydrocarbons, substituted phenols, and heavy metal ions from aqueous solutions. Distribution coefficients for polar aromatics can exceed 100. Applications include removal of Sr²⁺ and Cs⁺ from nuclear waste streams, Hg²⁺ and Pb²⁺ from environmental samples, and recovery of valuable organic products from aqueous reaction mixtures. ^[004]

3. Electrochemical Applications

With a wide electrochemical window of approximately 4.5 V and negligible vapor pressure, BMIM PF₆ serves as a non-volatile electrolyte in cyclic voltammetry, electrodeposition of reactive metals, and ionic liquid-gated field-effect transistors. Its thermal stability extends to ~300 °C, enabling high-temperature electrochemical studies. ^[005]

4. Gas Chromatography Stationary Phase

Coated on capillary columns (0.2–0.5 μm film thickness), BMIM PF₆ provides unique orthogonal selectivity for polar analytes. The dual retention mechanism combines partition (nonpolar interactions with the butyl chain and imidazolium ring) with hydrogen bonding and dipole interactions. Effective for separation of alcohols, aromatic hydrocarbons, essential oils, and PCBs with thermal stability to 200 °C. ^[005]

5. CO₂ Capture & Gas Separation

BMIM PF₆ and related imidazolium ionic liquids show selective CO₂ solubility — absorbing significant amounts of CO₂ at elevated pressures while rejecting N₂ and CH₄. This property is being explored for post-combustion carbon capture, natural gas sweetening, and biogas upgrading applications. ^[004]

Handling and Storage

GHS Hazard Statements:

- H302: Harmful if swallowed

- H315: Causes skin irritation

- H319: Causes serious eye irritation

- H335: May cause respiratory irritation

- H411: Toxic to aquatic life with long lasting effects

Signal Word: Warning

Pictograms: GHS07, GHS09

Storage: Store at room temperature in a tightly sealed container. Moisture-sensitive — store under inert gas (argon or nitrogen) for anhydrous applications. Protect from light. Avoid contact with strong oxidizing agents and strong bases. Thermal decomposition may produce HF and POₓ fumes — work in a fume hood. ^[002]

PPE: Wear appropriate chemical-resistant gloves (nitrile recommended), safety goggles with side shields, and a laboratory coat. Work in a well-ventilated area, preferably a fume hood. Use respiratory protection if handling large quantities or if the SDS indicates inhalation hazard. ^[002]

Always consult the Safety Data Sheet (SDS) from your supplier before handling. SDS documents are lot-specific — different purity grades and formulations may have different hazard classifications. For bulk handling, consult your institution's chemical hygiene plan and perform a job hazard analysis (JHA) before beginning work.

Regulatory & Compliance

Chemical Inventories: 1-Butyl-3-methylimidazolium Hexafluorophosphate (BMIM PF₆) (CAS 174501-64-5) is listed on major chemical inventories including the TSCA inventory in the United States, EINECS in the EU, and similar inventories in Japan (ENCS), China (IECSC), Korea (KECL), and Australia (AICS). Verify regulatory status with the appropriate national authority before importing, as inventory listings can change with regulatory updates. ^[004]

GHS Classification: Refer to the Handling and Storage section above for GHS hazard classification. National implementations (EU CLP Regulation, US OSHA HazCom 2012, China GB 30000 series) may have additional requirements. ^[002]

Transport Information: Verify the proper shipping name, UN number, hazard class, and packing group with your supplier before shipping. Transport regulations (IATA/ICAO for air, IMDG for sea, ADR/RID for road/rail) may impose quantity limits and packaging requirements. ^[004]

Frequently Asked Questions

What is the CAS number of 1-Butyl-3-methylimidazolium Hexafluorophosphate (BMIM PF₆)?

The CAS Registry Number is 174501-64-5. Always specify this CAS number when ordering to ensure correct compound identification, as chemical nomenclature can vary between suppliers and regions. ^[001]

What is the molecular weight of 1-Butyl-3-methylimidazolium Hexafluorophosphate (BMIM PF₆)?

The molecular weight is 284.18 g/mol, based on the molecular formula C₈H₁₅F₆N₂P. Use this value for stoichiometric calculations, solution preparation, and analytical method development. ^[001]

What are the main applications of 1-Butyl-3-methylimidazolium Hexafluorophosphate (BMIM PF₆)?

1-Butyl-3-methylimidazolium Hexafluorophosphate (BMIM PF₆) is primarily used for: Biphasic Catalysis & Catalyst Recycling; Liquid-Liquid Extraction; Electrochemical Applications. For detailed protocols and additional applications, see the Key Applications section above. ^[004]

How should 1-Butyl-3-methylimidazolium Hexafluorophosphate (BMIM PF₆) be stored?

Store at room temperature in a tightly sealed container. Moisture-sensitive — store under inert gas (argon or nitrogen) for anhydrous applications. Protect from light. Avoid contact with strong oxidizing agents and strong bases. Thermal decomposition may produce HF and POₓ fumes — work in a fume hood. Always refer to the Safety Data Sheet (SDS) from your specific supplier for the most accurate storage recommendations. ^[002]

Where can I buy 1-Butyl-3-methylimidazolium Hexafluorophosphate (BMIM PF₆)?

1-Butyl-3-methylimidazolium Hexafluorophosphate (BMIM PF₆) (CAS 174501-64-5) may be sourced through CoreyChem. Contact [email protected] with your CAS number, required quantity, and desired purity for sourcing assistance and a competitive quote. ^[003]

Where to Buy / Product Sourcing

1-Butyl-3-methylimidazolium Hexafluorophosphate (BMIM PF₆) (CAS 174501-64-5) is not currently listed in the CoreyChem catalog. Contact [email protected] for sourcing assistance. ^[003]

Our sourcing team can assist with procurement from qualified manufacturers worldwide. Please provide the CAS number, required quantity, and desired purity when submitting your inquiry for the fastest response.

References & Sources