All the processes by which metal complexes split the C-H bonds in hydrocarbons are considered. The problem of coordinating alkanes or alkyl groups in organic compounds with metal complexes is also considered. Methane when irradiated with light at 121.6 nm decomposes to generate hydrocarbons from which the stable products are formed. Studies have found that very weak alkane or alkyl adducts, in which the C-H bond is directly coordinated to the metal or its ligands, do not necessarily lead to subsequent cleavage of the C-H bond. The results of research studies have shown that transition metal complexes cleave the C-H bonds in ethylenes and acetylenes, in addition to the C-H bonds in arenes and alkanes. The complex MnH3(dmpe)2 is found to activate aromatic and benzylic C-H bonds under thermal and photochemical conditions.