1. Other reagents) than bridged ligan. The reason for this difference is presumably the exposed nature
of terminal ligands in contrast to bridged ligands that are surrounded by the protective influence of
the bulky Cp groups.
Equation 13.16 provides additional evidence that steric effects are important to the reactivity of
Ln(III) complexes. Hydrogenolysis is facile for complexes in which the ionic radius of the Ln(III) is
large. For Lu, the smallest of the lanthanides, the reaction is slow because the complex is now “
sterically saturated “ and the alkyl group is not accessible to H2.
The examples shown above demonstrate a salient characteristic of organolanthanide chemistry: in
spite of its inherent sameness, regardless of metal, a subtle adjustment in the steric bulk of ligands
surrounding the metal can make significant difference in the reactivity of the particular type of the
complex.This property is ....... to the lanthanides. Thus chemist, through a good understanding of the
relationship between degree of steric saturation and chemical reactivity,have been able in many
cases to design molecules with predictable reactivity.
Nevertheless, this understanding is stilln not complete. For examples, the.......... Cp*3Ln complex was
reported recently, where Ln = Sm ( equation 3.17 ). Previous thinking proposed that the Cp* ligand
would be too bulky for ..... such groups to surround a metal. The existence of the Sm complex
suggets that larger lanthanides such as Ce and Pr could also coordinate to three Cp* ligands and
provide stable Cp..Ln complexes. Synthesis of these awaits further research.
............................................................................................................................................
Although organolanthanide complexes do not undergo oxidative addition and reductive elimination,
they readly promote or catalyze order fundamental reactions such us 1,2-olefin insertion (section
10-6), sigma bond metathesis ( section