The first metal complexes containing the 1,4-cyclohexa-2,5-dienyl ligand (benzene 1,4-dianion); Synthesis and structures of [K(18-crown-6)][Ln{eta(5)-C5H3(SiMe(3))(2)(C6H6)] (Ln=La, Ce)

The reaction of [Ln{eta(5)-C5H3(SiMe(3))(2)-1,3}(3)] or [(Ln{eta(5)-C5H3(SiMe(3))(2)-1,3}(2)(mu-Cl))(2)] (Ln = La, Ce) with K or C8K and 18-crown-6 in benzene at ambient temperature yields the crystalline, deep red salts [K(18-crown-6)][Ln{eta(5)-C5H3(SiMe(3))(2)-1,3}(2)(C6H6)] (Ln = La 1, Ce 2), formulated as containing the. Ln(III)(1,4-cyclohexa-2,5-dienyl) moiety, on the basis of their X-ray structures, spectra and hydrolysis to give cyclohexa-1,4-diene.