Black, red, gold: The reaction of SeF4 with Me3SiN3 at low temperatures results in the formation of the first binary selenium(IV) azide Se(N3)4. The decomposition in an NMR tube shows the colors of gray selenium, red selenium, and the desired yellow selenium tetraazide (see picture). The reactions of [SeF5]− and [SeF6]2− with Me3SiN3 furnish the corresponding polyazidoselenites [Se(N3)5]− and [Se(N3)6]2−. All materials are extremely temperature‐sensitive.

The reaction of organoselenides and -diselenides (R2Se and (RSe)2) with XeF2 furnished the corresponding organoselenium(IV) difluorides R2SeF2 (R=Me (1), Et (2), iPr (3), Ph (4), Mes (=2,4,6-(Me)3C6H2) (5), Tipp (=2,4,6-(iPr)3C6H2) (6), 2-Me 2NCH2C6H4 (7)), and trifluorides RSeF3 (R=Me (8), iPr (9), Ph (10), Mes (11), Tipp (12), Mes* (=2,4,6-(tBu) 3C6H2) (13), 2-Me2NCH2C6H4 (14)), respectively. In addition to characterization by multinuclear NMR spectroscopy, the first molecular structure of an organoselenium(IV) difluoride as well as the molecular structures of subsequent decomposition products have been determined. The substitution of fluorine atoms with Me3SiN3 leads to the corresponding organoselenium(IV) diazides R2Se(N3)2 (R=Me (15), Et (16), iPr (17), Ph (18), Mes (19), 2-Me 2NCH2C6H4 (20)) and triazides RSe(N3)3 (R=Me (21), iPr (22), Ph (23), Mes (24), Tipp (25), Mes* (26), 2-Me2NCH2C6H4 (27)), respectively. The organoselenium azides are extremely temperature-sensitive materials and can only be handled at low temperatures.

The syntheses of the selenium containing heterocycles dibenzoselenophene (1 ≡ biphenSe) and dibenzo[1,2]diselenine (2 ≡ biphenSe2) were optimized. The halogenation reactions of 1 and 2 with XeF2, SO2Cl2, Br2 and I2 were performed and the corresponding products characterized. In the case of 1, the selenium(IV) dihalogenides, biphenSeF2 (3), biphenSeCl2 (4), biphenSeBr2 (5), and the adduct biphenSe·I2 (6), were isolated and identified. The extremely sensitive selenium(IV) difluoride 3 slowly formed significant amounts of an adduct with HF of the corresponding selenium(IV) oxide biphenSeO·HF (3a) upon storage in glass vessels at low temperatures. In the case of 2, the selenium(IV) trihalogenides, biphen(SeHal3)2 (Hal = F, Cl, Br), were found to be extremely labile (Hal = F) or not detectable (Hal = Cl, Br). Instead, as decomposition products, the selenium chloride species Se2Cl2, SeCl4 and 1 were detected. In the case of Hal = I, the stable adduct biphenSe2·I2 (7) was isolated. In addition to characterization by multinuclear NMR spectroscopy, several molecular structures of biphen‐selenium substituted halogenides were determined.

The preparation of Se(CN) 4 was attempted by the reaction of SeF 4 with Me 3SiCN at low temperatures. However, selenium tetracyanide could not be detected by NMR spectroscopy; instead, the decomposition product Se(CN) 2 was isolated and its crystal structure was redetermined. In the structure of Se(CN) 2, layers are present with secondary Se...N interactions. The structure of Se(CN) 4 and its reductive decomposition reaction has been calculated at the MP2 level of theory.

The tellurenyl fluoride, 2-Me 2 NCH 2 C 6 H 4 TeF, was obtained from reaction of the tellurenyl iodide RTeI with AgF. The compound was unambiguously identified by 19 F and 125 Te NMR spectroscopy. The decomposition under disproportionation leads to the tellurium(IV) trifluoride, 2-Me 2 NCH 2 C 6 H 4 TeF 3 and the ditelluride RTeTeR. The fluorination of the ditelluride, (2-Me 2 NCH 2 C 6 H 4 Te) 2 , with XeF 2 results in pure RTeF 3 . The molecular structure of 2-Me 2 NCH 2 C 6 H 4 TeF 3 , the second structural characterized tellurium(IV) trifluoride, has been determined. Furthermore the syntheses of the new tellurium(IV) difluoride, (2-6 ), was elucidated. Theoretical investigations for the compounds containing the stabilizing 2-dimethylaminomethylphenyl substituent are illustrated.