||Treatment of MH(OTf)(dppm)2 (M = Ru, Os) with CH2=C=CHR (R = Ph, nC5H11 and CO2Et) led to the formation of allyl complexes [Ru(η3-CH2CHCHR)(dppm)2]OTf. Treatment of OsH(OTf)(dppe)2 with CH2=C=CHR led to the formation of η2-coordinated complexes [OsH(η2-CH2=C=CHR)(dppm)2]OTf. Reactions of MH(OTf)(PP)2 (PP = dppm, dppe) with CH3CH=C=CHCO2Et gave either vinyl- or allyl products. The readily available and relatively cheap metal salt RuCl3 showed high efficiency in catalyzing C-H amination reactions of C-H bond of ortho-aryl phenylazides, 1-azido-2-arylvinylazides, and 1-azido-1,3-butadienes. Both computational and experimental results support that a two-step process involving formal electrocyclization is involved in the reaction mechanism. Treatments of metal cyclopentadienyl complexes with TlPF6 afforded thallium bridged trimetallic complexes. The in situ NMR experiments and theoretical studies support that a [(η5-C5H5)M(TlH)(PR3)2]+ or a [(η5-C5H5)M(TlH)(PR3)2]2(Tl)+ intermediate is involved in the reactions. A computation study showed that many metallabenzene complexes are thermodynamically unstable with respect to the correponding Cp complexes. However, stable metallabenzenes could be obtained by using proper choice of ligands, metals and substituents on the metallabenzene rings.