Divalent structures organometallic complexes

Giesbrecht, G.R., Cui, C.M., Shafir, A. etal. (2002) Divalent lanthanide metal complexes of atriazacyclonoane-functionalized tetramethylcyclopentadienyl ligand X-ray crystal structures of [C5Me4SiMe2( Pr2-tacn)]Lnl (Ln=Sm, Yb tacn=l,4-diisopropyl-l,4,7-triazacyclononane). Organometallics, 21, 3841. 

In this chapter we will review the synthesis, structural aspects, and basic chemical properties of formally divalent and trivalent titanium and zirconium metallocene complexes. We have restricted our coverage to the low-valent bis(rj-cyclopentadienyl) and related metallocenes metal halide complexes and organometallic mixed metal systems will not be discussed here. We have not attempted to present an exhaustive coverage of the field. Rather, our aim has been to describe critically and to evaluate the often confusing chemistry that has been reported for the reactive low-valent titanium and zirconium metallocenes. More general reviews (7) and a book (2) on the organometallic chemistry of titanium, zirconium, and hafnium have been published. 

Reduction of dinitrogen molecule by divalent lanthanide complexes has been a popular subject in coordination and organometallic chemistry of the lanthanide elements. In the course of these studies, a large number of polynuclear lanthanide clusters featuring a core of lanthanide atoms organized around a dinitrogen unit have been obtained and structurally characterized. 

Yao, Y Zhang, Y Zhang, Z. Shen, Q. Yu, K. Synthesis and structural characterization of divalent ytterbium complexes supported by fi-diketiminate ligands and their catalytic activity for the polymerization of methyl methacrylate. Organometallics 2003, 22, 2876-2882. 

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