Isoselenocyanates versus Isothiocyanates and Isocyanates

Abstract

Alkyl and aryl isoselenocyanates are well known intermediates in the synthesis of various organoselenium compounds, but the knowledge of the physicochemical properties of simple unsaturated derivatives is still fragmentary. Vinyl-, 2-propenyl-, and cyclopropyl isoselenocyanates have been prepared by reaction of selenium in powder with the corresponding isocyanides. The isoselenocyanates of this series, with a variable distance between the N═C═Se group and the unsaturated or pseudounsaturated group, have been studied by UV-photoelectron spectroscopy and quantum-chemical calculations. For each of these three isoselenocyanates, the exploration of conformers and geometrical optimization always converge toward only one local minimum. The vinyl and cyclopropyl derivatives are characterized by similar order of magnitude of interactions between the NCSe group and the substituent, while for allylic compound two noninteracting moieties should be considered. The same conclusions were obtained for vinylic and cyclopropylic sulfur and oxygen derivatives. Thus the type and extent of interactions between the N═C═X (X = O, S, Se) group and an unsaturated (vinyl, allyl, or cyclopropyl) moiety are now clarified.

Rotational Spectra and Structures of Phenyl Isocyanate and Phenyl Isothiocyanate

“…Finally, the derived C1-N and C7-N bond lengths and the ∠C1NC7 angles mirror those predicted 41 for vinyl-NCO and vinyl-NCS suggesting that the hybridization of the adjoining atom of the R group has a critical influence on the electronic structure at nitrogen. b CD constants in square brackets were fixed to the value from the parent.…”

“…From the derived geometries, this change results in shorter C−N bonds and a larger valence bond angle at nitrogen in PhNCS compared with PhNCO. Finally, the derived C1−N and C7−N bond lengths and the ∠C1NC7 angles mirror those predicted 41 for vinyl-NCO and vinyl-NCS suggesting that the hybridization of the adjoining atom of the R group has a critical influence on the electronic structure at nitrogen.…”

Conformers of Allyl Isothiocyanate: A Combined Microwave Spectroscopy and Computational Study

“…37 Similar results were observed in the benchmark study of the PES of the isovalent allyl-NCO compound, where among more than 20 functionals tested, dispersion uncorrected DFT methods failed to describe the proper conformational distribution. 11 Thus, although allyl-NCS was investigated previously using both computational 16,38 and experimental 14,15,16 methods, the present work is the first study to predict and confirm the presence of conformer I, the lowest energy conformation.…”

Polyselenoureas via Multicomponent Polymerizations Using Elemental Selenium as Monomer

“…Its synthesis proceeds via the multicomponent reaction of elemental selenium, isocyanides, and amines to form selenoureas with 100% atom economy. This process is analogous to isoselenocyanate chemistry, whereby isocyanides are reacted with elemental black selenium powder to form isoselenocyanates. , We demonstrate that this simple methodology proceeds rapidly under atmospheric conditions at ambient temperature in the presence of various amine monomers. Isoselenocyanates are generated in situ upon the reaction of the elemental selenium with the isocyanides, subsequently reacting with the amine moieties forming the selenourea linking motifs.…”