The reactions of cobaltadithiolene complexes bearing phenyl or ester l
igands with tetracyanoethylene oxide (TCNEO) result in the formation o
f dicyanomethylene-bridged complexes, via dicyanomethylide intermediat
es. Furthermore, the reaction of cobaltadithiolene complex bearing 4-p
yridyl ligands produces pyridinium dicyanomethylide complexes in good
yields.