Inorganic Chemistry, Vol.58, No.1, 188-198, 2019
Ammonium and Potassium Salts of a Hexacoordinate Phosphorus(V) Anion Featuring P-O and P-C Bonds
Ammonium and potassium salts featuring the chiral mer-[P(C6H4CO2)(3)](-), mer-[1](-), have been isolated. Specifically, treating phosphorane P(C6H4CO2)(2)(C6H4CO2H), 2, with N-containing bases [N-base = PhNMe2, PhNH2, pyridine (py), isoquinoline, (-)-brucine, N(n-C8H17)(3)] afforded ammonium salts [NbaseH](+)-mer-[1](-). Each compound was fully characterized spectroscopically, and four were subjected to X-ray crystallographic analysis. Salts were isolated with the racemic mixture of the mer-[1](-) anion except in the case of [(-)-brucineH]-Lambda-mer-[1], for which the crystal analyzed was enantiomerically pure. The potassium salt, K-mer-[1], was synthesized by treating 2 with KH. The solid-state structure of K-mer-[1] is a coordination polymer consisting of seven- and eight-coordinate K+ ions that are weakly bound by oxygen of either the racemic anion or the methanol solvent. Preliminary NMR and MS data for the formation of the Bronsted acid, H(DMF)(n)[1], has also been obtained. An estimate of the basicity of anion mer-[1](-) was obtained from IR measurements of the N-H stretching frequency for [(n-C-8-H-17)(3)NH]-mer-[1]. On the basis of these measurements, anion mer-[1](-) was ranked similar to the classical weakly coordinating anion, [ClO4](-), in terms of its coordinating ability.