Metathesis and diaziridination reactions of (CO)5W = C(OMe)-p-XC6H4 with cis-azobenzene. Electronic and solvent effects

Article abstract of DOI:10.1021/ja00039a029

The reaction of cis-azobenzene with a series of para substituted phenyl carbenes (CO)₅W=C(OMe)p-XC₆H₄ (X = H, OMe, CF₃) was carried out in both noncoordinating and coordinating solvents. The stability and reactivity of the initially formed zwitterionic species (CO)₅WNPhNPhC(OMe)(p-XC₆H₄) depended on the substituent X. In noncoordinating solvents, the unsubstituted zwittenonic species (CO)₅WNPhNPhC(OMe)C₆H₅ was converted into an isomeric zwitterionic intermediate and a 2,4-diazametallacycle. Both isomeric zwitterions and the 2,4-diazametallacycle ultimately decomposed to yield the metathesis product PhN=C(OMe)Ph. The mechanism of 2,4-diazametallacycle formation was shown to involve the intermediacy of a coordinated diazindine in which the metal subsequently inserts into the N-N bond. When the unsubstituted zwittenon was decomposed in CH₃CN, the coordinated diaziridine was displaced by solvent, inhibiting formation of the 2,4-diazametallacycle.