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 Ph2 P-BH2 ⋅NMe3 (1) and tBuHP-BH2 ⋅NMe3 (2). The corresponding monooxidation products Ph2 P(X)-BH2 ⋅NMe3 (X=O-Te, 3 a-d) and tBuHP(X)-BH2 ⋅NMe3 (X=O-Te, 4 a-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 O2 , S8 and Se yielding tBu(HX)P(X)-BH2 ⋅NMe3 (X=O, S, Se, 5 a-c). The telluride compounds presented herein are the first examples of neutral Te-substituted phosphanylboranes.