Reactivity of Complexes of 4fⁿ5d¹ and 4fⁿ⁺¹ Ln²⁺ Ions with Cyclooctatetraene

The Ln²⁺ complexes [K(2.2.2-cryptand)][Cp′₃Ln] (Ln = La, Ce, Pr, Nd, Sm, Eu, Dy, Tm, Yb; Cp′ = C₅H₄SiMe₃) were reacted with 1,3,5,7-cyclooctatetraene, C₈H₈, to determine if the reactivity of the complexes of 4fⁿ⁺¹ ions differed from that of 4fⁿ5d¹ ions. Crystallographically characterizable (C₈H₈)^2- complexes were obtained only for the larger metals in the lanthanide series, and two types of products were obtained: [K(2.2.2-cryptand)][Cp′₂Ln(C₈H₈)] (Ln = La, Ce) and [K(2.2.2-cryptand)][Ln(C₈H₈)₂] (Ln = Ce, Pr, Nd, Sm). The expected co-products of the two-electron reduction of C₈H₈ by 2 equiv of [K(2.2.2-cryptand)][Cp′₃Ln], namely, the tetrakis(cyclopentadienyl) complexes, [K(2.2.2-cryptand)][Cp′₄Ln], were crystallographically characterized for six metals (Ln = Ce, Pr, Nd, Sm, Dy, Tm).