Crystal structures of deoxygenation products and the characteristics of reactions of phenyl(trihalomethyl)mercury with tetraphenylcyclone

The single crystal structures of the gem-dihalides (3a and 3b) produced fro m the reactions of tetraphenylcyclone (TPCP) with phenyl(trihalomethyl)merc ury (trihalo = tribromo, bromodichloro) are reported. The structural parame ters of the X-ray single crystal analysis vary slightly with the radius of the halogen atom in dihalides and are found to be related to the yields of the deoxygenation products. These results support the proposed mechanism fo r the carbene reaction of this type and reflect the key role of the structu ral characteristics of the incipient carbonyl ylide intermediate in choosin g different competitive reaction pathways.