Heteroorganic betaines4. Photolysis and thermolysis of betaines containing the+P−C−Si−S− structural fragment

Photolysis and thermal decomposition of betaines R3P−CR1R2−SiR3R4−S− (1) follows two main pathways: (a) a Corey—Chaykovsky type reaction with elimination of Ph3P and generation of silathiirane[graphic not available: see fulltext] (2) and (b) a retro-Wittig type reaction accompanied by elimination of R3P=CR1R2 and generation of silanethione R3R4Si=S (3). Highly reactive compounds2 and3 undergo subsequent transformations to give derivatives of tetrahydro-1,4-dithia-2,5-disilin, 1,3-dithia-2,4-disilolane, and phosphonium salts ofsymm-tetraorganodisilthiane dithiolates [Ph3P+CHR1R2]2[(R3R4SiS−)2S]. The structures of the compounds obtained were established by X-ray diffraction analysis and multinuclear NMR spectroscopy.