The Nobel Prize for Chemistry in 2005 was awarded to the developing field of metathesis reactions using ruthenium complexes. The most widely used ruthenium complex is an olefin metathesis reaction used as a Grubbs catalyst in the reaction of ring opening polymerization (ROMP) and ring closing metathesis (RCM). These various organic synthesis reactions are possible due to ruthenium complexes having various oxidation states and coordination structures. Other representative examples of ruthenium complex reactions include metallacycle, vinylidene complex, π complex formation, oxidation/reduction reaction and others