Alkene transposition catalysis is mechanistically diverse and generally proceeds via either of the three alternative paths, namely, allyl, alkyl, or radical mechanisms with the latter two governing the activity of the vast majority of catalyst systems. In both mechanisms metal hydrides are the active species, which promote the transposition reaction via an H -/H • addition to the alkene followed by the β-H elimination/ H • -abstraction to furnish the isomerization product. 4c The representative examples operating via the alkyl mechanism such as Pd(dba) 2 (Skrydstrup), 7a Co-NNP complexes (Liu), 10f and Fe(OAc) 2 (Koh) 12b typically require the in situ activation to form the catalytic metal hydride species by the reaction with such reagents as e.g., acyl chloride, ammonia borane, boryl reagent combined with base. Activation-free olefin transpositions catalysis was also demonstrated with isolated metal hydride or metal alkyl complexes. With respect to the radical-type processes, the latest advances were disclosed by Shenvi and Palmer groups employing cobalt salen 10c and cobaloxime complexes, 10e respectively. Upon the reductive treatement, these complexes form Co hydrides that can act as H • -donors. The central role of the metal hydrides for the catalytic C=C bond suggests a potentially broader scope of catalyst systems for this chemistry.