Oxidation of Substituted Phosphanylboranes with Chalcogens

The elemental chalcogens sulfur, selenium, tellurium and bis(trimethylsilyl) peroxide as an oxygen source are applied for the oxidation of the phosphanylboranes Ph2P-BH2 center dot NMe3 (1) and tBuHP-BH2 center dot NMe3 (2). The corresponding monooxidation products Ph2P(X)-BH2 center dot NMe3 (X= O-Te, 3a-d) and tBuHP(X)-BH2 center dot NMe3 (X= O-Te, 4a-d) were obtained in good yields and comprehensively characterized by single crystal X-ray structure analysis, NMR, IR spectroscopy and mass spectrometry. The first oxidation step proceeds very selectively for all chalcogenides. For the tBu derivative, a further oxidation can be realised with O-2, S-8 and Se yielding tBu(HX) P(X)-BH2 center dot NMe3 (X= O, S, Se, 5a-c). The telluride compounds presented herein are the first examples of neutral Te-substituted phosphanylboranes.