Half-Sandwich Cerium and Lanthanum Dialkyl Complexes: Synthesis, Structure, and Reactivity Studies

Abstract

Cerium and lanthanum dialkyl complexes [η 5 -1,2,4-(Me 3 C) 3 C 5 H 2 ]Ln(CH 2 C 6 H 4 -o-NMe 2 ) 2 (Ln = Ce 1 and La 2), supported by a tri-tert-butylcyclopentadienyl ligand, have been successfully synthesized. Studies demonstrate that these complexes possess diverse reactivity toward various small molecules. For example, the reaction of complexes 1 and 2 with diphenyl dichalcogenides PhEEPh (E = S, Se) results in the formation of lanthanide thiolates5 and La 6), concomitantly releasing PhE(CH 2 C 6 H 4 -o-NMe 2 ). Furthermore, complexes 1 and 2, upon reaction with dibenzyl disulfide, yield tetranuclear rare-earth metallomacrocyclic compounds {[(η 5 -1,2,4-(Me 3 C) 3 C 5 H 2 )Ln(μ-SCH 2 C 6 H 5 )] 2 (μ−η 3 :η 3 -SCHC 6 H 5 )} 2 (Ln = Ce 7 and La 8). This reaction may involve a process of σ-bond metathesis and C−H activation. While the reaction of 1 and 2 with dibenzyl diselenide in the presence of LiCH 2 C 6 H 4 -o-NMe 2 leads to the formation of lanthanide-lithium selenido clusters [(η 5 -1,2,4-(Me 3 C) 3 C 5 H 2 )La(μ-SeCH 2 C 6 H 5 )] 3 (μ 3 -Se)[μ 3 -SeLi(THF) 3 ] (Ln = Ce 9 and La 10). Meanwhile, lanthanide selenido clusters [(η 5 -1,2,4-(Me 3 C) 3 C 5 H 2 )La(μ-SeCH 2 C 6 H 4 -o-NMe 2 )] 4 (μ 3 -Se) 2 (Ln = Ce 11 and La 12) can be obtained by treating 1 and 2 with elemental selenium in a 1:2 molar ratio. Additionally, the treatment of 1 and 2 with benzoxazole generates ring-opening/C−C coupling/C−N coupling products {(η 5 -1,2,4-(Me 3 C) 3 C 5 H 2 )La[μ-OC 6 H 4 -o-N�CHN(CH(CH 2 C 6 H 4 -o-NMe 2 ) 2 C 6 H 4 -o-O]} 2 (Ln = Ce 13 and La 14). All new compounds were characterized by various spectroscopic methods, and their solid-state structures were confirmed by single-crystal X-ray diffraction analyses.