Fluorochemicals from fluorspar via a phosphate-enabled mechanochemical process that bypasses HF

Abstract

All fluorochemicals-including elemental fluorine and nucleophilic, electrophilic, and radical fluorinating reagents-are prepared from hydrogen fluoride (HF). This highly toxic and corrosive gas is produced by the reaction of acid-grade fluorspar (>97% CaF₂) with sulfuric acid under harsh conditions. The use of fluorspar to produce fluorochemicals via a process that bypasses HF is highly desirable but remains an unsolved problem because of the prohibitive insolubility of CaF₂. Inspired by calcium phosphate biomineralization, we herein disclose a protocol of treating acid-grade fluorspar with dipotassium hydrogen phosphate (K₂HPO₄) under mechanochemical conditions. The process affords a solid composed of crystalline K₃(HPO₄)F and K_2-<i>_x</i>Ca<i>_y</i>(PO₃F)<i>_a</i>(PO₄)<i>_b</i>, which is found suitable for forging sulfur-fluorine and carbon-fluorine bonds.