Preparation of N(SeCl)2+X–(X = SbCl6 or FeCl4), F3CCSeNSeCCF3+SbCl6–, F3CCSeNSeCCF3, F3CCSeNSeCCF3 and F3CCSeSeC(CF3)C(CF3)SeSeCCF3. Electron diffraction study of F3CCSeSeCCF3 and crystal structure of the eight-membered heterocycle F3CCSeSeC(CF3)C(CF3)SeSeCCF3

Abstract

The salts N(SeCl)₂⁺SbCl₆^–1 and N(SeCl)₂⁺FeCl₄^–2 were synthesized by reaction of SeCl₃⁺ X^–(X = SbCl₆ or FeCl) with N(SiMe₃)₃; 1 was also formed by reaction of Se₂NCl₃ with SbCl₅. Reaction of 1 with SnCl₂ and F₃CCCCF₃ led to the formation of F₃C[graphic omitted]CF₃⁺ SbCl₆^–3. In this reaction the Se₂N ⁺ cation is a likely intermediate because SnCl₂ seems to be essential for chloride abstraction in the first reaction step to generate Se₂N⁺in situ which then adds F₃CCCCF₃ to yield 3. Compound 3 is a useful building block to generate selenium compounds such as F₃C[graphic omitted]CF₃4, F₃C[graphic omitted]CF₃5 and F₃C[graphic omitted]CF₃6. The heterocycle 5 was shown by electron diffraction to have an approximately planar four-membered ring structure. The structure of compound 6 was determined by X-ray crystallography: orthorhombic, space group Pbca, a= 10.1920(21), b= 13.0615(20) and c= 22.050(5)Å. In order to rationalize the structures of 5 and the cation F₃C[graphic omitted]CF₃⁺, ab initio calculations were made on model compounds in which the CF₃ groups were replaced by a fluorine atom (i.e.F[graphic omitted]F for 5and F[graphic omitted]F⁺ for the cation in 3). In addition, mass spectrometric experiments were performed in order to examine the structures and stabilities of the unligated cation F₃C[graphic omitted]CF₃⁺ as well as its neutral counterpart. The existence of the neutral radical 4 was established by means of neutralization–reionization mass spectrometry.