Chapter 6 - Organometallic Complexes

Abstract

This chapter discusses organometallic complexes of rare earths. The 4f orbitals in the lanthanides are well shielded and the metals do not experience an effective nuclear charge as the 5p, 6s, or 5d orbitals. In spite of this, the 4f orbitals become more attractive with an increase in atomic number which results in a decrease in radius, also known as the “lanthanide contraction”. By the loss of 4f electrons, La attains a stable electronic configuration giving rise to a trivalent oxidation state. The lanthanides in 4+ oxidation state are strong oxidizing agents and an example is Ce4+. Organolanthanides are predominantly ionic due to the inability of forbitals to overlap with ligand molecular orbitals and because of the exceptional stability of the trivalent state of lanthanides, oxidative-addition reaction is not favored. The large radii of lanthanides require sterically demanding ligands to form discrete monomeric compounds. Most of the organometallic complexes of lanthanides contain one Π donor/ Π acceptor type of ligand along with other ligands such as halides, hydrides, alkyls, and so on and the latter are the reactive centers of catalytic reactions.