Rare-earth mediated dihydrogen activation and catalytic hydrogenation

This review covers H–H bond cleavage of dihydrogen (H₂) mediated by structurally well-defined rare-earth metal (scandium, yttrium and lanthanides) complexes, and their applications in homogenous catalysis, such as catalytic hydrogenation of unsaturated organic molecules. Depending on the mechanism of the H–H bond cleavage, this review is organized in two parts: (1) σ-bond metathesis, and (2) non-σ-metathesis H₂ activation. The latter is a new trend in this research field and is the emphasis of this review. Converting H2 into inorganic rare-earth polyhydride complexes, albeit their potential applications as hydrogen-storage materiel, is not in the scope of this review.