Generation and Spectroscopic Identification of Selenofulminic Acid and Its Methyl and Cyano Derivatives (XCNSe, X=H, CH₃, NC)

Abstract

Evidence for the existence of nitrile selenides, potential 1,3-dipolarophiles in cycloaddition reactions, has been provided by direct spectroscopic methods. The parent nitrile selenide, selenofulminic acid (HCNSe), and its methyl and cyano derivatives have been photolytically generated in an inert solid argon matrix from 1,2,5-selenadiazoles by 280, 254, and 313 nm UV irradiation, respectively, and studied by ultraviolet spectroscopy and mid-infrared spectroscopy. Ground-state geometries have been obtained from quantum-chemical calculations at the CCSD(T)/aug-cc-pVTZ level. Nitrile selenides are predicted to be linear with a relatively weak N-Se bond.

Generation and Spectroscopic Identification of ClCNS, ClNCS and NCCNS

“…The sulfur atom also has no absorption at this wavelength. Nitrile sulfides, however, have a characteristic UV band in this region; HCNS20 and CH 3 CNS7 show UV bands at 208 and 209 nm, respectively, and FCNS20 at 206 and 350 nm. Formation of FCNS in the case of 3‐chloro‐4‐fluoro‐1,2,5‐thiadiazole must be negligible, because its most characteristic UV band at 350 nm is not observed, and the formation of HCNS in the case of 3‐chloro‐1,2,5‐thiadiazole can be excluded on the basis of IR spectroscopic investigations (see below).…”

“…They were generated in the matrix by 254 nm UV irradiation of 1,2,5-thiadiazole and 3,4-difluoro-1,2,5-thiadiazole, respectively. Corresponding inorganic seleno compounds (HCNSe and NCCNSe) [6] were generated similarly from the appropriate 1,2,5-selenadiazoles last year. Although photochemical nitrile elimination from 1,2,5-thiadiazoles is expected to be a novel and general synthetic route for nitrile sulfides, substituent effects may alter the photochemical properties and may lead to unexpected products.…”

Structure, Stability, and Cycloaddition Reactions of Nitrile Selenides

“…The photochemical instability of HCNSe, NCCNSe, and CH 3 CNSe in cryogenic argon matrices was observed recently. [5] The calculated barriers for the rupture of N-Se bonds in the excited triplet state are 0, 53, 20, 16, 0, and 3 kJ mol À1 (DG 0K ) for HCNSe, FCNSe, ClCNSe, BrCNSe, NCCNSe, and CH 3 CNSe, respectively, at the CCSD(T)//B3LYP level.…”

“…[1,2] However, small nitrile selenides (X ¼ H, CH 3 , Ph, Cl, Br, I, NC, CH 3 S) have been synthesized and identified as neutral species in the gas phase by neutralizationreionization mass spectroscopy, [3,4] which additionally provided evidence for their existence with lifetimes of at least microseconds in the dilute gas phase. Considering direct spectroscopic methods, the existence of only four derivatives namely, HCNSe, [5] NCCNSe, [5] CH 3 CNSe, [5] and PhCNSe, [6,7] has been proven by UV and IR spectroscopy in inert noble gas matrices at low temperatures; three of the four derivatives were discovered only in the last year. All of these molecules were synthesized from 1,2,5-selenadiazole derivatives under narrowband UV irradiation.…”

Photochemical Formation of Diazenecarbaldehyde (HNNCHO) and Diazenecarbothialdehyde (HNNCHS) in Low-Temperature Matrices

“…Due to the latter advantage MI spectra can be straightforwardly correlated both with spectra obtained by quantum chemical computations and by astrophysical observations. Therefore, it is not surprising that MI spectroscopy has been extensively applied to generate and characterize reactive molecules with astrochemical interest. − …”