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.

Figure optionsDownload as PowerPoint slide