Polycondensation of Tris(Trimethylsilylseleno)Phosphane

Abstract

Tris-(trimethylsilyl)phosphane and their organo substituted derivatives (Me₃Si)_3−nP(Me₃C)_n (n: 0, 1, 2) (la-c) had been found suitable for the insertion of selenium into the phosphorus-silicon bond. At deep temperatures all silylselenophosphanes of the series (Me₃SiSe)_3−nP(Me₃C_n) (2a-c) are formed in a nearly quantitative reaction, if no excess selenium is present. (Me₃C)(Me₃SiSe)₂P=Se (3b) and (Me₃C)₂(Me₃SiSe)P=Se (3c) are detectable in small quantities as the only by-products of the reaction of (Ib-c), whereas (la) end in the formation of (2a) and traces of the dimer (Me₃SiSe)₂P-P(SeSiMe₃)₂ (4). On exposure to light or at elevated temperatures (2a) undergoes a disproportionation, forming Se=P(SeSiMe₃)₃ (3a), and the heterocycles P₃Se₄(SeSiMe₃) (5) and α-P₄Se₃(SeSiMe₃)₂ (6). (Me₃Si)₂Se is spUt off as a condensation product. After further irradiation or prolonged standing at room temperature, an insoluble oligomer is formed. The constitutions of (2-6) were determined by the analysis of their ³¹P- and ⁷⁷Se-nmr spectra.