Synthesis and controlled hydrolysis of organolanthanide complexes with mono- and dianionic benzimidazole-2-thiolate ligands

Abstract

Treatment of Cp₃Er with one equivalent of benzimidazole-2-thiol (H₂Bzimt) in THF affords the monoanionic HBzimt⁻ complex Cp₂Er(η²-HBzimt)(THF)₂ (1). Reaction of Cp₃Yb with two equivalents of H₂Bzimt gives complex CpYb(η²-HBzimt)₂(THF) (2) at room temperature. Treatment of Cp₃Ln with three equivalents of H₂Bzimt in reflux THF affords the homoleptic Ln(η²-HBzimt)₃(THF)₂ (Ln = Er (3), Y (4)). Cp₃Ln reacts with 0.5 equivalents of H₂Bzimt to afford the dianionic Bzimt²⁻ complexes [(Cp₂Ln)(THF)]₂(μ-Bzimt) (Ln = Yb (5), Er (6), Dy (7), Y (8)) in good yields, in which the Bzimt²⁻ ligand bridges the two metals in an μ-η²:η² coordination mode. Interestingly, controlled hydrolysis of complexes Cp₂Ln(η²-HBzimt)(THF)₂, CpLn(η²-HBzimt)₂(THF) and [(Cp₂Ln)(THF)]₂(μ-Bzimt) produces the same tetranuclear complexes [CpLn(μ₃-OH)(μ-η¹:η²-HBzimt)]₄ (Ln = Yb (9), Er (10), Y (11)), indicating that the hydrolysis selectivity greatly depends on the number of coordinated cyclopentadienyl groups. All complexes were characterized by elemental analysis, spectroscopic properties and X-ray single crystal diffraction analysis.