C2-Symmetric ansa-Lanthanidocene Complexes. Synthesis via Silylamine Elimination and β-SiH Agostic Rigidity

The synthesis as well as the spectroscopic and structural characterization of a new class of C2-symmetric, mononuclear metallocene complexes of the lanthanide elements is described. Heteroleptic lanthanidocene silylamide complexes have been obtained ate-complex-free according to silylamine elimination reactions of complexes Ln[N(SiHMe2)2]3(THF)x (x = 1, Ln = Sc; x = 2, Ln = Y, La, Nd, Lu) and linked, substituted cyclopentadiene and indene systems. The molecular structure of [Me2Si(C5Me4)2]La[N(SiHMe2)2] (95% isolated yield) has been determined by X-ray crystallography. Brintzinger-type, indenyl-derived metallocene complexes have been isolated in racemic yields as high as 72%. IR and multinuclear NMR spectroscopy (1H, 13C, 29Si, 89Y) reveals the presence of an unprecedented strong diagostic interaction between the electron-deficient metal centers and the SiH moiety of the bis(dimethylsilyl)amide ligand:  SiH stretching vibrations as low as 1759 cm-1 and 1JSi,H coupling constants as low as 133 Hz indicate a...