The hydrogen fluoride solvent system. Part IV. Solutions of mercury(II) cyanide. Evidence for the Hg2(CN)3+ cation

Abstract

Cryoscopic, conductimetric, and spectroscopic methods have been used to study solutions of Hg(CN)₂ in anhydrous HF. It is concluded that mercury(II) cyanide ionises in the following manner (a). The cation Hg₂(CN)₃⁺ probably 2Hg(CN)₂+ 2HF ⇌ Hg₂(CN)₃⁺+ HCN + HF₂^–(a) has a linear cyanide bridged structure [NC–Hg–CN–Hg–CN]⁺. Further ionisation to give HgCN⁺ can also occur according to the equation (b). However the HgCN⁺ ion is not formed in appreciable amounts except in the Hg₂(CN)₃⁺+ 2HF ⇌ 2HgCN⁺+ HCN + HF₂^–(b) presence of Lewis acids, e.g., BF₃ and AsF₅, which precipitate the insoluble salts HgCN⁺BF₄^– and HgCN⁺AsF₆^–. These salts were isolated and characterised.