TRISPHAT

Tributylammonium TRISPHAT is the an organic salt with the formula [(C₄H₉)₃NH]+[P(O₂C₆Cl₄)^3-]. The anion features phosphorus(V) bonded to three tetrachlorocatecholate (C₆Cl₄O₂^2-) ligands. This anion can be resolved into the enantiomers, which are optically stable (the picture shows the Δ enantiomer).

The TRISPHAT anion has been used as a “chiral shift reagent” for cations. It improves the resolution of ¹H NMR spectra by forming diastereomeric ion pairs.

Preparation

The anion is prepared by treatment of phosphorus pentachloride with tetrachlorocatechol followed by a tertiary amine gives the anion:

PCl₅ + 3 C₆Cl₄(OH)₂ → H[P(O₂C₆Cl₄)₃] + 5 HCl

H[P(O₂C₆Cl₄)₃] + Bu₃N Bu₃NH⁺ [P(O₂C₆Cl₄)₃]^- Using a chiral amine, the anion can be readily resolved.

References