Stereochemistry of Electrophilic or Homolytic Substitutions

When studying metal atom exchange in the acetylene quasi-complexes formulated as metal chlorovinyls, Borisov and the author found that the chlorovinyl group retained its configuration during the reactions. Some of them, e.g., 

The rule was quickly confirmed, cis or /ra/w-j3-Chlorovinylmercury chloride treated with radioactive ° HgCl2 rapidly produced the Hg-mercurated chlorovinylmercury chlorides but the configurations were strictly retained 129). 

The remarkable reaction discovered by Reutov, the fast exchange of bis(chlorovinyl)mercury with metallic ° Hg, helped us to show that this apparently homolytic process involved fast insertion of Hg and complete retention of the configuration 129). 

in collaboration with Borisov, we extended the rule to cover a wider class of organometallics, cis- and traK5-CgH5CH=C(M)CjH5 and cis- and /raK5-CH3CH=CHM, where M is Li, Hg, Tl, Sn 130-132). The cycles of electrophilic and homolytic reactions performed did not reveal any exception to the rule, which was also shown to be true when applied to the reactions of cis- and tran -propenyllithium with typical organic compounds, i.e., aldehydes, ketones, and CO2 133, 122). 

When we were undertaking this work NMR spectroscopy had not been discovered. Later, reinvestigating the compounds using NMR, we found 

---