Benzyl complexes of rare earth metals

Data on the synthesis, structure, and reactivity of benzyl complexes of rare earth elements in the oxidation state +3 are integrated and analyzed. A variety of methods for the synthesis of homoleptic tris(benzyl) derivatives and heteroleptic mono- and bis(benzyl) complexes containing spectator ligands of various nature and denticity are considered. The attention is focused on the structure of LnIII benzyl derivatives in the crystalline state. It is shown that the mode of coordination of the benzyl ligand to Ln3+ ions depends on the ionic radius and steric congestion of the metal center, as well as on the ligand nature and can vary from κ1-Cα- to poly-hapta-coordination due to the non-valent interactions of the metal center with the ipso- and ortho-atoms of the aromatic ring.