RARE-EARTH COMPLEXES WITH HETEROALLYLIC LIGANDS AND THEIR USE AS PRECURSORS FOR LANTHANIDE-BASED HOMOGENEOUS CATALYSTS

Bulky heteroallylic ligands are shown to be very promising alternatives for cyclopentadienyl ligands in lanthanide chemistry. In particular, the easily accessible silylated benzamidinate ligands [RC6H4C(NSiMe3)2]- (NCN) may soon rival C5H5- and CMe5- in their high versatility. Heteroallylic ligands are capable of stabilizing reactive lanthanide(II) complexes (eg. [RC6H4C(NSiMe3)2]2Yb(THF)2 (1, 2)) as well as homoleptic complexes of the type [RC6H4C(NSiMe3)2]3Ln, the latter being useful precursors for lanthanide-based materials (Ln2O3, Ln2S3, Ln2Se3). Of special interest for future applications are functionalizable bis(ligand) lanthanide halides and triflates (eg. [Ph2P(NSiMe3)2]2LnCl(THF) (II) and [RC6H4C(NSiMe3)2]2Y(O3SCF3) (18)). Implications for the development of novel homogeneous catalysts are discussed.