,3-dimethylcyclopropane (both isomers), anti-6-bromo-syn-6-trimethyltinbicyclo[3.1.0] hexane,7-bromo-7-trimethyltinnorcarane, and also the 7-triphenyltin-, 7-trimethyllead- and 7-triphenyllead- derivatives (both isomers), 1-bromo-1-trimethyltinspiro[2.5]octane and 9-bromo-9-trimethyltinbicyclo[6.1.0] nonane (both isomers) has been studied. Under the conditions used, the syn-Me3Sn isomers decomposed