CYCLOADDITION REACTIONS OF ALDEHYDES TO TETRAMESITYLDISILENE AND TETRAMESITYLGERMASILENE - EVIDENCE FOR A BIRADICAL INTERMEDIATE

The mechanism of the addition of aldehydes to disilenes and germasilen es was investigated by examining the reaction between trans-(2-phenylc yclopropyl)carboxaldehyde and tetramesityldisilene or tetramesitylgerm asilene. tyl(2-cis-4-trans-1-oxa-5-phenylpentadienyl)silyl] dimesityls ilane (1) and tetramesityl-4-phenyloxa-2,3-disilacyclohept-6-ene (2) w ere formed in the reaction between the aldehyde and the disilene, and the analogous tyl(2-cis-4-trans-1-oxa-5-phenylpentadienyl)silyl] dimes itylgermane (4) and ramesityl-4-phenyloxa-2,3-silagermacyclohept-6-ene (5) were formed in reaction with the germasilene. It is proposed that compounds 1, 2, 4, and 5 are the result of either disproportionation or ring closure of an intermediate biradical derived from initial bond formation between the oxygen atom of the aldehyde and the doubly bond ed silicon atom of the dimetallene.