Lanthanocene Chemistry with [CpR]-, [Cpt]-, [Cptt]-, and [CpR‘2SiMe2]2-Ligands: Synthesis and Characterization of Bis(cyclopentadienyl)lanthanide(III) Halides and Bis(cyclopentadienyl)lanthanide(II) Complexes and Crystal Structures of [{NdCpR2(μ-Cl)}2], [{TmCptt2(μ-I)}2], and [Yb(CpR‘2SiMe2)(THF)2] (CpR= η5-C5H4{CH(SiMe3)2}, Cpt= η5-C5H4(SiMe2But), Cptt= η5-C5H3(SiMe2But)2-1,3, and CpR‘= η5-C5H3{CH(SiMe3)2}-3)

The bis(substituted cyclopentadienyl)lanthanide(III) halides [{LnCp R 2 (μ-Cl)} 2 ] (Ln = Pr, Nd, Sm, Dy, Tb, Y), [{LnCp tt 2 (μ-X)} 2 ] (X = Cl, Ln = La, Nd; X = I, Ln = Tm), and [Nd(Cp R ‘ 2 SiMe 2 )(μ-Cl)} 2 ] and bis(substituted cyclopentadienyl)lanthanide(II) complexes [LnCp R 2 (THF) 2 ] (Ln = Sm, Eu, Yb), [YbCp t 2 (THF) 2 ], [LnCp tt 2 (THF) 2 ] (Ln = Sm, Yb), LnCp R 2 (Ln = Sm, Eu, Yb), YbCp t 2, LnCp tt 2 (Ln = Sm, Yb), and [Yb(Cp R ‘ 2 SiMe 2 )(THF) 2 ] (Cp R = η 5 -C 5 H 4 {CH(SiMe 3 ) 2 }, Cp t = η 5 -C 5 H 4 (SiMe 2 Bu t ), Cp tt = η 5 -C 5 H 3 (SiMe 2 Bu t ) 2 -1,3 and Cp R ‘ = η 5 -C 5 H 3 {CH(SiMe 3 ) 2 }-3) have been synthesized from the appropriate LnCl 3, TmI 3, or LnI 2 with the selected sodium or potassium cyclopentadienide. The complexes were characterized by 1 H, 13 C, 29 Si, and 171 Yb (for Yb(II) complexes) NMR spectroscopy, elemental analysis, and mass spectrometry. The molecular structures of [{NdCp R 2 (μ-Cl)} 2 ], [{TmCp tt 2 (μ-I)} 2 ], and [Yb(Cp R ‘ 2 SiMe 2 )(THF) 2 ] have been determined by single-crystal X-ray diffraction studies. Attempts to reduce the complexes [{NdCp R 2 (μ-Cl)} 2 ], [{NdCp tt 2 (μ-Cl)} 2 ], and [{TmCp tt 2 (μ-I)} 2 ] are described.