Reactivity studies on lanthanum and cerium hydrido metallocenes

Abstract

Alkyl complexes [η⁵-1,3-(Me₃C)₂C₅H₃]₂Ln(CH₂C₆H₄-o-NMe₂) (Ln = La 1 and Ce 2) react with 9-borabicyclo[3.3.1]nonane (9-BBN) in THF to afford the lanthanum boroxide complex [η⁵-1,3-(Me₃C)₂C₅H₃]₂La(μ-OBC₈H₁₄)(THF) (3) and cerium boroxide complex [η⁵-1,3-(Me₃C)₂C₅H₃]₂Ce(μ-OBC₈H₁₄)(THF) (4). However, the reaction of alkyl complexes [η⁵-1,3-(Me₃C)₂C₅H₃]₂Ln(CH₂C₆H₄-o-NMe₂) with cyclohexene oxide followed by the addition of 9-BBN resulted in the formation of ring-opened products [η⁵-1,3-(Me₃C)₂C₅H₃]₂Ln(OC₆H₁₁)(THF) (Ln = La 5 and Ce 6) concomitant with C₈H₁₄BCH₂C₆H₄N(CH₃)₂ release, indicating that lanthanum and cerium hydride complexes formed in situ by treating alkyl complexes with 9-BBN may be the reactive species. Therefore, further studies on the reactivity of lanthanum and cerium hydride complexes generated in situ were carried out. The reaction of lanthanum and cerium hydride complexes with Me₃SiCl provided lanthanide chloride complexes [η⁵-1,3-(Me₃C)₂C₅H₃]₂LnCl (Ln = La 7and Ce 8) as well as Me₃SiH. Each lanthanide hydride complex reduces phenazine and white phosphorus to produce {[η⁵-1,3-(Me₃C)₂C₅H₃]₂Ln}₂(μ–η³:η³-C₁₂H₈N₂) (Ln = La 9 and Ce 10) and {[η⁵-1,3-Me₃C)₂C₅H₃]₂Ln}₃P₇ (Ln = La 11 and Ce 12), respectively. All the new compounds were characterized by various spectroscopic methods, and their solid-state structures were further confirmed by single-crystal X-ray diffraction analyses.