Synthesis and reactivity of cationic lanthanide metallocene complexes. Hexabromocarborane and tetraphenylborate as counter ions

摘要

Treatment of unsolvated Cp "(2)Ln(II) [Cp " = 1,3-(Me3Si)(2)C5H3] with 1 equivalent of Ag(I)Y, or reaction of [Cp "(2)LnI](2) with 2 molar equivalents of Ag(CB11Br6H6) in pure toluene at room temperature gave "Lewis base-free" cationic lanthanide metallocene complexes [Cp "(2)Ln]Y (Y = BPh4-, Ln = Sm 1, Yb 2. Y = CB11Br6H6 Ln = Sm 3, Er 4) in good yield. They slowly undergo decomposition reaction at room temperature. The reactivity of these "Lewis base-free" cationic complexes is highly dependent upon the coordinating nature of the counter ions. Complexes 3 and 4 are much more reactive than 1 and 2. Recrystallization of 1 and 2 from 1,2-dimethoxyethane (DME) and THF yielded [Cp "Sm-2(DME)][BPh4] 5 and [Cp "Yb-2(THF)(2)][BPh4] 6, respectively. However, recrystallization of 3 and 4 from THF resulted in the ring-opening polymerization of THE The THF coordinated complexes [Cp "(2)Ln(THF)(2)][CB11Br6H6] (Ln = Sm 7, Er 8) were isolated via recrystallization of 3 and 4 from toluene containing a small amount of THE The "Lewis base-free" cation ''Cp "Er-2(+)" can abstract one bromine atom from the counter ion CB11Br6H6- or one chlorine atom from CH2Cl2 to form [Cp "2ErBr](2) or [Cp "2ErCl](2), respectively. Unfortunately, these cations do not exhibit reactivity towards 1-hexene at room temperature. Molecular structures of 5, 7, 8 and [Cp "2ErBr](2) have been confirmed by single-crystal X-ray analyses. [References: 47]