The metalladithiolene ring in [CpCo(SィイD22ィエD2CィイD22ィエD2XY)]-type dithiolatocobalt complexes show a variety of reactivities due to unsaturation and due to aromaticity. The rings undergo the addition reactions which are ascribed to the unsaturation (multi bond plicity) between the metal and sulfur atoms in the metalladithiolene rings. Dimethyl acetylenedicarboxylate, quadricyclanc, diazo compounds, and azide compounds which were able to use as precursors of reactive intermediates bridge between metal and sulfur to form alkene-, norbornene-, alkylidene-, and imido-bridged adducts.
In this work, our attention was focused especially on alkylidene and imido-bridged adducts from the standpoint of capture and elimination of reactive intermediates on the metalladichalcogenolene rings. They further react with Lewis bases and protic acids, resulting in the opening of the three-membered rings in adducts to afford the corresponding three-component adducts. Interestingly, the bond cleaved is dependent on the attacking reagents and on the structures of the bridging groups.
We investigated in detail the electrochemical behavior of alkylidene- and imido-bridged adducts and their three-component adducts, together with their photochemical behavior and their thermal activation with chemical reagents. As a topic, the reaction of the sulfonylimido-bridged addut with triphenylphosphine resulted in the migration of imido group to the cyclopentadienyl ring. From a cross over experiment, the rearrangement has been concluded to be an intermolecular reaction, suggesting the participation of nitrene species.