SYNTHESIS AND REACTIVITY OF CATIONIC LANTHANIDE METALLOCENE COMPLEXES- HEXABROMOCARBORANE AND TETRAPHENYLBORATE AS COUNTER IONS

Treatment of unsolvated Cp ''(2)Ln(II) [Cp '' = 1,3-(Me3Si)(2)C5H3] wi th 1 equivalent of Ag(I)Y, or reaction of [Cp ''(2)LnI](2) with 2 mola r equivalents of Ag(CB11Br6H6) in pure toluene at room temperature gav e ''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 temper ature. 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. Recrystallizati on 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 p olymerization 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 cati ons do not exhibit reactivity towards 1-hexene at room temperature. Mo lecular structures of 5, 7, 8 and [Cp ''2ErBr](2) have been confirmed by single-crystal X-ray analyses.