Cerocene and Lanthanocene Chalcogenides: Synthesis, Structure, and Luminescence

A series of lanthanide chalcogenides {[η⁵-1,3-(Me₃C)₂C₅H₃]₂Ln}₂(μ-η²:η²-Te₂) (Ln = Ce 1, La 2), {[η⁵-1,3-(Me₃C)₂C₅H₃]₂Ln(THF)}₂(μ-Se) (Ln = Ce 3, La 4), and {[η⁵-1,3-(Me₃C)₂C₅H₃]₂Ln(THF)}₂(μ-Te) (Ln = Ce 5, La 6) can be readily obtained by the reaction of the alkyl complexes [η⁵-1,3-(Me₃C)₂C₅H₃]₂Ln(CH₂C₆H₄-o-NMe₂) with elemental selenium or tellurium in the presence of 9-borabicyclo[3.3.1]nonane (9-BBN). The reaction of the alkyl complexes [η⁵-1,3-(Me₃C)₂C₅H₃]₂Ln(CH₂C₆H₄-o-NMe₂) with 9-BBN in 1:2 molar ratio afforded the lanthanide (cyclooctane-1,5-diyl)dihydroborate complexes [η⁵-1,3-(Me₃C)₂C₅H₃]₂Ln[(μ-H)₂BC₈H₁₄] (Ln = Ce 7, La 8) concomitant with the (Me₂N-o-C₆H₄CH₂)BC₈H₁₄ release, indicating that [η⁵-1,3-(Me₃C)₂C₅H₃]₂LnH may be the reactive species for the synthesis of lanthanide chalcogenides. 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. Luminescence spectroscopy was also employed to characterize complexes 1-6. The Ce(III) complexes 3 and 5 display distinct luminescence properties at room temperature, as compared to the corresponding La(III) complexes 4 and 6. The complex {[η⁵-1,3-(Me₃C)₂C₅H₃]₂Ce(THF)}₂(μ-Te) (5) exhibits unexpectedly red emission in solution which is found to depend strongly on the excitation wavelength.