Terphenyl Cyclooctatetraenyl Compounds of Samarium

The syntheses and molecular structures of a number of terphenyl-based compounds of the lanthanide element samarium are reported. Reaction of 2 equiv of DppLi (Dpp = 2,6-diphenylphenyl) with 1 equiv of SmCl₃ in tetrahydrofuran at room temperature yields (Dpp)₂SmCl(μ-Cl)Li(THF)₃ (1). The one-pot reaction of 1 equiv of K₂COT (COT^2- = cyclooctatetraenyl dianion) with 1 equiv SmCl₃ in tetrahydrofuran at room temperature followed by addition of 1 equiv of terphenyllithium salt DppLi, DmpLi (Dmp = 2,6-dimesitylphenyl), or DanipLi (Danip = 2,6-di(o-anisol)phenyl) produces DppSmCOT(μ-Cl)Li(THF)₃ (2), DmpSm(THF)COT (3), and DanipSm(THF)COT (4), respectively. In the case of the Danip-based compound 4 the order of addition of reagents can be reversed producing the same compound, however, in considerably lower yield. Compound 2 can also be prepared by reaction of 1 with 1 equiv of K₂COT in tetrahydrofuran. The molecular structure of the bis(terphenyl) compound 1 exhibits a formally four-coordinate metal atom. The molecular structures of the terphenyl COT compounds 2−4 feature monomeric complexes which are obtained either as a lithium chloride adduct (2) or as tetrahydrofuran adducts (3, 4). In 4 the Danip ligand adopts the meso form.