The discoveries that soluble transition metal complexes are able to cleave unactivated C-H bonds were made in 1960s by Kleiman and Dubeck,as well as Chatt and Davidson.These findings stimulated widespread hope in an entirely new field of organic synthesis where the manipulation of unreactive C-H bonds became a possibility.Extensive progress has been made during 30 years,and as a result,more than 50 review articles have appeared,mostly dealing with the stoichiometric cleavage of C-H bonds by metal complexes.In contrast to the rich chemistry of these stoichiometric reactions,the development of catalytic reactions using this chemistryhas been very slow,till 1990s.