Dimeric hydride complexes of rare-earth metals containing a linked amido-cyclopentadienyl ligand: Synthesis, characterization, and monomer-dimer equilibrium

Dimeric hydride complexes of lutetium, ytterbium, and yttrium containing a linked amido-cyclopentadienyl ligand, [Ln(eta (5):eta (1)-C5Me4SiMe2NCMe2R)(L)mu -H)](2) (Ln = Lu, Yb, Y; R = Me, Et; L = THF, PMe3), were synthesized and characterized by elemental analysis and H-1, C-13 Si-29,and P-31 NMR spectroscopy. A single-crystal X-ray diffraction study of [Yb(eta (5):eta (1)-C5Me4-SiMe2NCMe2Et)(THF)(mu -H)](2) showed a homochiral dimeric structure with a trans configuration of the ancillary ligands, in analogy to the related yttrium complex. The PMe3 adducts of lutetium and yttrium [Ln(eta (5):eta (1)-C5Me4SiMe2NCMe3)(PMe3)(u-H)](2) (Ln = Lu, Y) were prepared in low yields by substitution of THF with a large excess of PMe3, Their crystal structures were determined and revealed a cisoid configuration of the linked amido-cyclopentadienyl ligands, isotypic with the scandium analogue previously described by Bercaw et al. On the NMR time scale fast dissociation of the Lewis base L is observed. Scrambling of the yttrium and lutetium hydride complexes [Ln(eta (5):eta (1)-C5Me4SiMe2NCMe3)(THF)(mu -H)](2) (Ln = Lu, Y) in C6D6 gave a mixture containing the heterobimetallic species [LUY(eta (5):eta (1)-C-5-Me4SiMe2NCMe3)(2)(THF)(2)(mu -H)(2)] within 5 min, indicating the presence of monomeric species in solution. Chloro hydride complexes of yttrium, [{Y(eta (5):eta (1)-C5Me4SiMe2NCMe2R)(THF)}(2)-(mu -H)(mu -Cl)], were formed by scrambling the chloro complex with the hydride complex for 3 h. The dimeric chloro complexes [Y(eta (5):eta (1)-C5Me4SiMe2NCMe2R)(THF)(mu -Cl)](2) could be synthesized by reacting in situ formed ''Y(CH2SiMe3)(2)Cl(THF)(n)" with the amino-cyclopentadiene (C5Me4H)SiMe2NHCMe2R in a sigma -bond metathesis. Single-crystal X-ray diffraction studies showed the chloro complex [Y(eta (5):eta (1)-C5Me4SiMe2NCMe2Et)(THF)(mu -Cl)](2) to adopt a trans configuration of the ancillary ligands as a heterochiral dimer, whereas the chloro hydride [{Y(eta (5):eta (1)-C5Me4SiMe2NCMe2Et)(THF)}(2)(mu -H)(mu -Cl)] was found to be a homochiral dimer.