Formation and reaction of three-membered cobaltathiaziridine ring in (η5-cyclopentadienyl)(substituted imido-κN-thio-κS-ethene-2-thiolato-κS)cobalt(III). Ring opening and closure and transfer of imido group

Three-membered cobaltathiaziridine rings are formed in the reactions of [CpCo{S2C2(COOMe)2}] either with some azides (RN3: p-toluenesulfonyl azide (TsN3), methanesulfonyl azide (MsN3), and ethyl azidoformate (EtOOCN3)) or with N-(phenyliodonio)-p-toluenesulfonamidate (PhI=NTs) to afford imido-bridged complexes, [CpCo{S2C2(COOMe)2}(NR)]. The ring undergoes unique ring opening and reforming reactions. Hydrogen chloride brings about the cleavage of the CoN bond to give S-iminodithiolatocobalt(III) complexes [Cp(Cl)Co{S(NR)C(COOMe)C(COOMe)S)}], which very easily regenerates the cobaltathiaziridine ring on treatment with bases, such as pyridine and even with the very weak base, water. The reaction with triphenylphosphine at room temperature results in the ring opening to give an ylide. The heating of a benzene solution of the ylide at 80°C (under reflux) gives a product in which a sulfonylimido moiety migrates to a carbon atom of the cyclopentadienyl ring. The reduction halfwave potential values of the imido-bridged complexes depend on the substituent of bridging moiety. The CV of sulfonylimido-bridged complex shows one-electron two-step reduction processes. We found that the reductant of the original complex is regenerated not by the first reduction, but by the second reduction according to CV and OTTLE measurements.