Dimeric Hydrido Complexes of Rare-Earth Metals Containing a Linked Amido−Cyclopentadienyl Ligand:  Synthesis, Characterization, and Monomer−Dimer Equilibrium

Dimeric hydrido complexes of lutetium, ytterbium, and yttrium containing a linked amido−cyclopentadienyl ligand, [Ln(η 5:η 1 -C 5 Me 4 SiMe 2 NCMe 2 R)(L)(μ-H)] 2 (Ln = Lu, Yb, Y; R = Me, Et; L = THF, PMe 3 ), were synthesized and characterized by elemental analysis and 1 H, 13 C 29 Si, and 31 P NMR spectroscopy. A single-crystal X-ray diffraction study of [Yb(η 5:η 1 -C 5 Me 4 SiMe 2 NCMe 2 Et)(THF)(μ-H)] 2 showed a homochiral dimeric structure with a trans configuration of the ancillary ligands, in analogy to the related yttrium complex. The PMe 3 adducts of lutetium and yttrium [Ln(η 5:η 1 -C 5 Me 4 SiMe 2 NCMe 3 )(PMe 3 )(μ-H)] 2 (Ln = Lu, Y) were prepared in low yields by substitution of THF with a large excess of PMe 3 . 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 hydrido complexes [Ln(η 5:η 1 -C 5 Me 4 SiMe 2 NCMe 3 )(THF)(μ-H)] 2 (Ln = Lu, Y) in C 6 D 6 gave a mixture containing the heterobimetallic species [LuY(η 5:η 1 -C 5 Me 4 SiMe 2 NCMe 3 ) 2 (THF) 2 (μ-H) 2 ] within 5 min, indicating the presence of monomeric species in solution. Chloro hydrido complexes of yttrium, [{Y(η 5:η 1 -C 5 Me 4 SiMe 2 NCMe 2 R)(THF)} 2 (μ-H)(μ-Cl)], were formed by scrambling the chloro complex with the hydrido complex for 3 h. The dimeric chloro complexes [Y(η 5:η 1 -C 5 Me 4 SiMe 2 NCMe 2 R)(THF)(μ-Cl)] 2 could be synthesized by reacting in situ formed “Y(CH 2 SiMe 3 ) 2 Cl(THF) n ” with the amino−cyclopentadiene (C 5 Me 4 H)SiMe 2 NHCMe 2 R in a σ-bond metathesis. Single-crystal X-ray diffraction studies showed the chloro complex [Y(η 5:η 1 -C 5 Me 4 SiMe 2 NCMe 2 Et)(THF)(μ-Cl)] 2 to adopt a trans configuration of the ancillary ligands as a heterochiral dimer, whereas the chloro hydrido [{Y(η 5:η 1 -C 5 Me 4 SiMe 2 NCMe 2 Et)(THF)} 2 (μ-H)(μ-Cl)] was found to be a homochiral dimer.