Chemoselective reduction of organoselenocyanates to diselenides and selenolates

Selenocyanates produce selenolates or diselenides on reaction with metal hydrides (NaH, LiHBEt, LiBH, NaBH). The former transformation is performed with 2 molar equivalents of sodium hydride or lithium triethyl borohydride or 1.25 molar equivalent of metal borohydrides. The second one is performed with lower amount of reducing agent (1 molar equivalent of sodium hydride or lithium triethyl borohydride or 0.25 equivalent of metal borohydrides). Intermediate formation of a selenol or a selenolate which reacts on the unreacted selenocyanate is suspected in the later transformation.