Cyclooctatetraenyl complexes of the early transition metals and lanthanides: Part XII. New sandwich and half-sandwich complexes of the lanthanides containing cyclooctatetraenyl ligands

The crystal structure of [(COT)Ce(μ-O3SCF3)(THF)2]2 (1) (COT=η8-C8H8) has been determined by X-ray diffraction. The compound crystallizes in the triclinic space group (a=930.7(4), b=1274.4(7), c=1864.1(10) pm; α=97.68(6), β=101.01(2), γ=105.25(1)°; Z=2). Together with the bridging triflate ligands the cerium atoms form an eight-membered Ce2O4S2 ring. Treatment of 1 with 2 equiv. of K[1,3-tBu2C5H3] affords the mixed-sandwich complex (COT)Ce(η5-1,3-tBu2C5H3) (2) in 78% yield. Furthermore, the preparation of a series of new lanthanide half-sandwich complexes containing the 1,4-bis(trimethylsilyl)cyclooctatetraenyl ligand (=COT″) and additional heteroallylic, aryloxide, and alkyl ligands is reported.