Lanthanocene and Cerocene Alkyl Complexes: Synthesis, Structure, and Reactivity Studies.

Abstract

Lanthanocene and cerocene alkyl complexes [η5-1,3-(Me3C)2C5H3]2Ln(CH2C6H4-o-NMe2) (Ln = La 3 and Ce 4) were obtained from the salt metathesis of {[η5-1,3-(Me3C)2C5H3]2Ln(μ3-κ3-O3SCF3)2K(THF)2}2·THF (Ln = La 1·THF and Ce 2·THF) with LiCH2C6H4-o-NMe2. Reactivity of 3 and 4 toward various small molecules provides access to a series of lanthanide derivatives. For example, reactions of 3 and 4 with elemental chalcogens (sulfur and selenium) in 1:1 molar ratio give the lanthanide thiolates {[η5-1,3-(Me3C)2C5H3]2Ln(μ-SCH2C6H4-o-NMe2)}2 (Ln = La 5 and Ce 6) and selenolates {[η5-1,3-(Me3C)2C5H3]2Ln(μ-SeCH2C6H4-o-NMe2)}2 (Ln = La 7 and Ce 8). The compounds 3 and 4 react with two equivalents of elemental chalcogens (sulfur and selenium) to afford the lanthanide disulfides {[η5-1,3-(Me3C)2C5H3]2Ln}2(μ-η2:η2-S2) (Ln = La 9 and Ce 10) and diselenides {[η5-1,3-(Me3C)2C5H3]2Ln}2(μ-η2:η2-Se2) (Ln = La 11 and Ce 12). The lanthanide disulfides (9 and 10) or diselenides (11 and 12) can also be readily obtained through oxidation of the corresponding lanthanide thiolates (5 and 6) or selenolates (7 and 8) by elemental chalcogens concomitant with the (Me2N-o-C6H4CH2)2E2 (E = S or Se) release. Treatment of 3 and 4 with one equivalent or two equivalents of benzonitrile produces the serendipitous lanthanum and cerium-1-azaallyl complexes [η5-1,3-(Me3C)2C5H3]2Ln[N(H)C(Ph)═CHC6H4-o-NMe2] (Ln = La 13 and Ce 14) or amidine complexes [η5-1,3-(Me3C)2C5H3]2Ln[N(H)C(Ph)NC(Ph)═CHC6H4-o-NMe2]·C7H8 (Ln = La 15·C7H8 and Ce 16·C7H8), respectively. The compound 15 or 16 can also be readily synthesized by further insertion of one benzonitrile molecule into the 1-azaallyl complex 13 or 14. Insertion of N,N'-dicyclohexylcarbodiimide or phenyl isothiocyanate into Ln-C bonds within 3 and 4 results in the formation of the amidine complexes [η5-1,3-(Me3C)2C5H3]2Ln[CyNC(CH2C6H4-o-NMe2)NCy] (Cy = cyclohexyl, Ln = La 17 and Ce 18) or thioamidato complexes [η5-1,3-(Me3C)2C5H3]2Ln[SC(CH2C6H4-o-NMe2)NPh] (Ln = La 19 and Ce 20). All of the new compounds were characterized by various spectroscopic methods, and their solid-state structures were further confirmed by single-crystal X-ray diffraction analyses.