Sodium tetrakis pentafluorophenyl borate
[CAS# 149213-65-0]

Identification

• Classification: Organic raw materials >> Organic fluorine compound >> Fluorophenylboric acid series
• Name: Sodium tetrakis pentafluorophenyl borate
• Molecular Formula: C₂₄BF₂₀Na
• Molecular Weight: 702.03
• CAS Registry Number: 149213-65-0
• EC Number: 873-010-3
• SMILES: [B-](C1=C(C(=C(C(=C1F)F)F)F)F)(C2=C(C(=C(C(=C2F)F)F)F)F)(C3=C(C(=C(C(=C3F)F)F)F)F)C4=C(C(=C(C(=C4F)F)F)F)F.[Na+]

Safety Data

• Hazard Symbols: GHS07 Warning
• Hazard Statements: H315-H319-H335-H413
• Precautionary Statements: P261-P264-P264+P265-P271-P273-P280-P302+P352-P304+P340-P305+P351+P338-P319-P321-P332+P317-P337+P317-P362+P364-P403+P233-P405-P501

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Chronic hazardous to the aquatic environment	Aquatic Chronic	4	H413
Skin irritation	Skin Irrit.	2	H315
Specific target organ toxicity - single exposure	STOT SE	3	H335
Eye irritation	Eye Irrit.	2	H319

Discovory and Applicatios

Sodium tetrakis(pentafluorophenyl)borate is an organoboron compound consisting of a boron center coordinated to four pentafluorophenyl groups, with sodium serving as the counterion. Its chemical formula is commonly represented as NaB(C₆F₅)₄. The compound belongs to the class of weakly coordinating anions and is widely recognized for its unique stability and low nucleophilicity due to the electron-withdrawing effects of the pentafluorophenyl substituents.

The synthesis of sodium tetrakis(pentafluorophenyl)borate typically involves the reaction of boron halides or boron trifluoride adducts with pentafluorophenyl organometallic reagents such as lithium or magnesium pentafluorophenyl derivatives. Subsequent salt metathesis with sodium salts yields the desired sodium tetrakis(pentafluorophenyl)borate. The highly fluorinated aromatic rings contribute to the remarkable chemical inertness of the borate anion, making it resistant to nucleophilic attack and hydrolysis.

This compound gained prominence in the late 20th century, particularly in organometallic and coordination chemistry, as a source of a weakly coordinating anion. Such anions are essential for stabilizing reactive cationic species without participating in side reactions. Sodium tetrakis(pentafluorophenyl)borate serves as a counterion to a variety of transition metal complexes and main group cations, enabling studies and applications that require stable but non-interfering ionic partners.

One of the primary applications of sodium tetrakis(pentafluorophenyl)borate is in homogeneous catalysis. It is employed to generate and stabilize highly electrophilic cationic metal catalysts used in olefin polymerization, hydroamination, hydrosilylation, and other important catalytic transformations. The anion’s weakly coordinating nature allows the metal center to maintain high reactivity and accessibility to substrates, improving catalytic efficiency and selectivity.

In addition, sodium tetrakis(pentafluorophenyl)borate is used in ionic liquid formulations and as a component in electrochemical systems due to its high thermal stability and chemical inertness. Its presence in electrolytes can enhance conductivity and stability under harsh conditions.

The compound is also utilized in the preparation of boron-based ionic liquids and salts with tailored physical and chemical properties for specific applications in materials science and catalysis. Its perfluorinated aromatic substituents impart hydrophobicity and stability, which are advantageous in diverse chemical environments.

Handling sodium tetrakis(pentafluorophenyl)borate requires standard precautions for air- and moisture-sensitive compounds because the anion can undergo hydrolysis under strongly acidic or aqueous conditions, though it is generally more stable than many other borate species. It is typically stored under inert atmosphere and used in anhydrous solvents.

In summary, sodium tetrakis(pentafluorophenyl)borate is a key weakly coordinating anion in modern chemistry, valued for stabilizing reactive cationic species in catalysis and materials science. Its synthesis, stability, and unique properties continue to support advances in organometallic chemistry and beyond.

References

2003. Phase-transfer Catalysis in Electrophilic Substitution Reactions: IX. Kinetics and Mechanism of Nitration of Polycyclic Arenes under Conditions of Phase-transfer Catalysis in a System Benzene-Aqueous Sulfuric Acid-Sodium Nitrite, Russian Journal of Organic Chemistry (39)
DOI: 10.1023/b:rujo.0000013130.89990.1e