Preparation of SeNSNSe(AsF6)2 and structural characterisation of the 6π‘electron-rich aromatic’ SeNSNSe2+

Abstract

Highly crystalline [graphic omitted]e(AsF₆)₂ was prepared by the oxidation of ([graphic omitted]e)₂(AsF₆)₂ with AsF₅ in liquid SO₂. The X-ray crystal structure was determined which consists of discrete planar [graphic omitted]e²⁺ cations and AsF₆^– anions with significant cation–anion interactions. The average Se–N [1.70(2)], S–N [1.59(1)] and Se–Se [2.310(2)Å] bond distances are consistent with the removal of the unpaired electron from the π* singly occupied molecular orbital of the 7π [graphic omitted]e˙⁺. The ⁷⁷Se [–70 °C, δ(Me₂Se)= 2411.7, v_½= 10.2 Hz] and ¹⁴N NMR [r.t., δ(MeNO₂)=–72.5, v_½= 690 Hz] and Raman spectrum in AsF₃ solution are all consistent with retention of the ring structure in solution. The reaction of Se₄(AsF₆)₂ and S₄N₄ was reinvestigated and found to give appreciable amounts of ([graphic omitted])₂(AsF₆)₂ and ([graphic omitted])₂(AsF₆)₂ as well as the reported ([graphic omitted]e)₂(AsF₆)₂. A pure sample of ([graphic omitted]e)₂(AsF₆)₂ was prepared by reduction of [graphic omitted]e(AsF₆)₂ with CsN₃.