Facile synthesis of tetraaryl phosphonium ionic liquids

Abstract

The syntheses of triphenyl-2-pyridylphosphonium salts, [Mopyphos]A, where A^- = BF₄^-, B(C₆H₅)₄^-, (CF₃SO₂)₂N^-, Sac^-, and Ace^-. (Sac^- = saccharinate, Ace^- = acesulfamate) are described. These salts can be synthesized on a multi-gram scale with good yields and have been characterized by NMR, single crystal XRD, and HRMS. Thermal analyses indicate that the bistriflimide (Tf₂N^- = (CF₃SO₂)₂N^-) salts are especially amenable towards high-temperature ionic liquid (IL) applications with decomposition temperatures above 450°C. The synthetic methods described herein can be utilized to generate several phosphonium bistriflimide ILs of the general formula [(C₆H₅)₃P-Ar]Tf₂N, where Ar = N-heteroaryl).