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TRISPHAT

TRISPHAT (full name tris(tetrachlorocatecholato)phosphate(1−)) is an inorganic anion with the formula often prepared as the tributylammonium () or tetrabutylammonium ( salt. The anion features phosphorus(V) bonded to three tetrachlorocatecholate () ligands. This anion can be resolved into the axially chiral 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 <sup>1</sup>H 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:

PCl<sub>5</sub> + 3 C<sub>6</sub>Cl<sub>4</sub>(OH)<sub>2</sub> → H[P(O<sub>2</sub>C<sub>6</sub>Cl<sub>4</sub>)<sub>3</sub>] + 5&nbsp;HCl
H[P(O<sub>2</sub>C<sub>6</sub>Cl<sub>4</sub>)<sub>3</sub>] + Bu<sub>3</sub>N → Bu<sub>3</sub>NH<sup>+</sup> [P(O<sub>2</sub>C<sub>6</sub>Cl<sub>4</sub>)<sub>3</sub>]<sup>−</sup>

Using a chiral amine, the anion can be readily resolved.

References