PREPARATION OF N(SECL)(2)(-) (X=SBCL6 OR FECL4), F3CCSENSECCF3+SBCL6-, F3CCSENSECCF3, F3CCSESECCF3 AND F3CCSESEC(CF3)C(CF3)SESECCF3 - ELECTRON-DIFFRACTION STUDY OF F3CCSESECCF(3) AND CRYSTAL-STRUCTURE OF THE 8-MEMBERED HETEROCYCLE F3CCSESEC(CF3)C(CF3)SESECCF3()X()

The salts N(SeCl)+SbCl6- 1 and N(SeCl)(2)(FeCl4-)-Fe-+ 2 were synthesi zed by reaction of SeCl,(+)X(-) (X = SbCl6 or FeCl4) with N(SiMe(3))(3 );1 was also formed by reaction of Se2NCl3 with SbCl5. Reaction of 1 w ith SnC2 and F3CCCCF3 led to the formation of F3CCSeNSeCCF3+SbCl6- 3. In this reaction the Se2N+ cation is a likely intermediate because SnC l2 seems to be essential for chloride abstraction in the first reactio n step to generate Se2N+ in situ which then adds F3CCCCF3 to yield 3. Compound 3 is a useful building block to generate selenium compounds s uch as F,CCSeNSeCCF, 4, F3CCSeSeCCF3 5 and F3CCSeSeC(CF3)C(CF3)SeSeCCF 3 6. The heterocycle 5 was shown by electron diffraction to have an ap proximately planar four-membered ring structure. The structure of comp ound 6 was determined by X-ray crystallography: orthorhombic, space gr oup Pbca, a = 10.1920(21), b = 13.0615(20) and c = 22.050(5) Angstrom. In order to rationalize The structures of 5 and the cation F3CCSeNSeC CF3+, ab initio calculations were made on model compounds in which the CF3 groups were replaced by a fluorine atom (i.e. FCSeSeCF for 5 and FCSeNSeCF+ for the cation in 3). In addition, mass spectrometric exper iments were performed in order to examine the structures and stabiliti es of the unligated cation F3CCSeNSeCCF3+ as well as its neutral count erpart. The existence of the neutral radical 4 was established by mean s of neutralization-reionization mass spectrometry.