Polarographic study of η2-acetylenic derivatives of cymanthrene

The electrochemical reduction of η2-acetylenic derivatives of cymanthrene CpMn(CO)2-(PhC=CR) (R=H, Ph, SiPh3, and GePh3) proceeds in three consecutive steps. The addition of one electron in the first step leads to the elimination of the acetylenic ligand, which is reduced in the subsequent steps. The nature of R does not affect the course of the electrochemical reaction and is only slightly reflected in the reduction potential values.