Tetraphenylborate

Tetraphenylborate refers to the anion [B(C₆H₅)₄]⁻, commonly encountered as its sodium salt, sodium tetraphenylborate, NaB(C₆H₅)₄. This anion is characterized by a central boron atom bonded to four phenyl groups. Sodium tetraphenylborate is a white crystalline solid that is sparingly soluble in water but more soluble in organic solvents like acetone and methanol.

The tetraphenylborate anion is a bulky, weakly coordinating anion. This property makes it useful in various chemical applications. For instance, it is employed as a precipitating agent for large, monovalent cations, particularly in analytical chemistry. It can also be used as a counterion in the synthesis of coordination complexes and organometallic compounds, where its weakly coordinating nature helps to stabilize reactive metal centers. Furthermore, tetraphenylborate salts are utilized in electrochemical studies and as phase transfer catalysts.

The synthesis of sodium tetraphenylborate typically involves the reaction of a phenyl Grignard reagent (phenylmagnesium bromide) with a boron halide, such as boron trifluoride. The resulting tetraphenylborate anion is then isolated as a salt. Due to its low solubility in water, it is often used to precipitate other metal cations from aqueous solutions, allowing for their separation and quantification.