Lanthanocene chemistry with [Cp-R](-), [Cp-t](-), [Cp-tt](-), and [(Cp2SiMe2)-Si-R '](2-) ligands: Synthesis and characterization of bis(cyclopentadienyl)lanthanide(III) halides and bis(cyclopentadienyl)lanthanide(II) complexes and crystal structures of [{NdCp2R(mu-Cl)}(2)], [{TmCp2tt(mu-I)}(2)], and [Yb((Cp2SiMe2)-Si-R ')(THF)(2)] (Cp-R = eta(5)-C5H4{CH(SiMe3)(2)}, Cp-t = eta(5)-C5H4(SiMe2But), Cp-tt = eta(5)-C5H3(SiMe2But)(2)-1,3, and Cp-R ' =eta(5)-C5H3{CH(SiMe3)(2)}-3)

The bis(substituted cyclopentadienyl)lanthanide(III) halides [{LnCp(2)(R)(m u-Cl)}(2)] (Ln = Pr, Nd, Sm, Dy, Tb, Y), [{LnCp(2)(tt)(mu-X)}(2)] (X = Cl, Ln = La, Nd; X = I, Ln = Tm), and [Nd-{((Cp2SiMe2)-Si-R')(mu-Cl)}(2)] and b is(substituted cyclopentadienyl)lanthanide(II) complexes [LnCp(2)(R)-(THF)( 2)] (Ln = Sm, Eu, Yb), [YbCp2t(THF)(2)], [LnCp(2)(tt)(THF)(2)] (Ln = Sm, Yb ), LnCp(2)(R) (Ln = Sm, Eu, Yb), YbCp2t, LnCp(2)(tt) (Ln = Sm, Yb), and [Yb ((Cp2SiMe2)-Si-R')(THF)(2)] (Cp-R = eta(5)-C6H4-{CH(SiMe3)(2)}, Cp-t = eta( 5)-C5H4(SiMe2BUt), Cp-tt = eta(5)-C5H3(SiMe2But)(2)-1,3 and Cp-R' = eta(5)- C5H3-{CH(SiMe3)(2)}-3) have been synthesized from the appropriate LnCl(3), TmI3, or LnI(2) with the selected sodium or potassium cyclopentadienide. Th e complexes were characterized by H-1, C-13, Si-29, and Yb-171 (for Yb(II) complexes) NMR spectroscopy, elemental analysis, and mass spectrometry. The molecular structures of [{NdCp2R(mu-Cl)}(2)], [{TmCp22tt(mu-I)}(2)], and [ Yb(Cp-2(R')-SiMe2)(THF)(2)] have been determined by single-crystal X-ray di ffraction studies. Attempts to reduce the complexes [{NdCp2R(mu-Cl)}(2)], [ {NdCp2tt(mu-Cl)}(2)], and [{TmCp2tt(mu-I)}(2)] are described.