A 77Se NMR study of elemental selenium reduction using NaBH4

•An in-depth analysis of inorganic selenide anions 77Se NMR is reported.•Selenium anions species not detected by 77Se NMR could be trapped by alkylation.•Dialkyl selenides, dialkyl diselenides or alkylselenols were selectively obtained.•77Se NMR spectra for organic and inorganic selenide anions is reported.

Alkylation or arylation of selenide or diselenide anions is a well-established method to obtain organoselenium compounds. Nevertheless, detecting inorganic selenium anions using 77Se NMR is still a challenge. In a previous work, alkylation of Na2Se was found sometimes to yield a mixture of organyl selenides/diselenides in variable amounts. In the literature, this mixture is sometimes attributed to the oxidation of an intermediate alkyl selenol during the extraction. To understand this process, a series of experiments using 77Se NMR were performed. It was clear from the 77Se NMR experiments that NaHSe− and Se22− formation was very dependent on the NaBH4 stoichiometry used. After alkylation, alkyl selenol and dialkyl diselenide were identified, proving they were not formed during the extraction step. As a result, alkyl selenols, dialkyl selenides or dialkyl diselenides with a high purity degree were obtained. To achieve high purity and selectivity of the organoselenium compound, the stoichiometric ratio between Se0/NaBH4 has to be carefully measured.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slide