Heteroorganic betaines 4. Photolysis and thermolysis of betaines containing the P+-C-Si-S- structural fragment

Photolysis and thermal decomposition of betaines R3P-(CRR2)-R-1-(SiRR4)-R-3 -S- follows two main pathways: (a) a Corey-Chaykovsky type reaction with el imination of Ph3P and generation of silathiirane (RRC)-R-1-C-2-(SiRR4)-R-3- S (2) and (b) a retro-Wittig type reaction accompanied by elimination of R3 P=(CRR2)-R-1 and generation of silanethione (RRSi)-R-3-Si-4=S (3). Highly r eactive compounds 2 and 3 undergo subsequent transformations to give deriva tives of tetrahydro-1,4-dithia-2,5-disilin, 1,3-dithia-2,4-disilolane, and phosphonium salts of symm-tetraorganodisilthiane dithiolates [(Ph3P+CHRR2)- R-1](2)[((RRSiS-)-R-3-Si-4)(2)S]. The structures of the compounds obtained were established by X-ray diffraction analysis and multinuclear NMR spectro scopy.