PARAMAGNETIC INTERMEDIATES IN THE PHOTOLYSIS OF 7-SILANORBORNADIENE STUDIED BY MEANS OF SPIN CHEMISTRY METHOD

The influence of an external magnetic held on the yield of photo-decom position products of 7,7'-dimethyl-7-silanorbornadiene derivative has been detected in laser pulse photolysis experiments. The observations of magnetic held effects alterations in the presence of scavengers, O- 2 and PPh3, in combination with H-1-CIDNP data form the basis for the identification of the structure of paramagnetic intermediates involved in the process. It has been shown that magnetic field effects origina te in biradical intermediates. These species result from both endocycl ic Si-C bond cleavage in the initial compound and the reaction of dime thylsilylene (in a singlet or a triplet excited state) with starting 7 -silanorbornadiene. To explain the influence of O-2 upon the magnetic held effects, the reversible formation of oxygen complex with biradica l species has been suggested. (C) 1998 Elsevier Science S.A. All right s reserved.