Synthesis and studies on reactivities of tetrahydrofurfurylcyclopentadienyl lanthanide chlorides CpsLnCl2·2THF (Ln=Dy, Ho, Gd) and Cps2LnCl·(Ln=Sm, Dy). The crystal structures of Cps2SmCl and Cps2Sm·(C3N2HMe2)

Reactions of lanthanide trichloride with two or one equivalent of tetrahydrofurfurylcyclopentadienyl (Cps) sodium salt in THF afford bis(tetrahydrofurfurylcyclopentadienyl)lanthanide chloride complexes Cps2LnCl [Ln=Sm (1), Dy (2)] and mono(tetrahydrofurfurylcyclopentadienyl)lanthanide dichloride complexes CpsLnCl2·2THF [Ln=Dy (3), Ho (4), Gd (5)], respectively. Treatment of 1 with one equivalent of NaPzMe2 (PzMe2=3,5-dimethylpyrazolate) forms Cps2SmPzMe2 (6). Complex 3 reacts with one equivalent of CpNa to yield the mixed-ring complex [CpsCpDyCl]2 (7). Complexes 1–7 have been characterized by elemental analyses, infrared and mass spectroscopies. The X-ray structural analyses show that 1 and 6 are unsolvated monomers. In complex 1, the Sm atom is surrounded by two Cps rings, one chlorine atom and two oxygen atoms of the side-chain to form a distorted trigonal bipyramid. The coordination number of central metal is nine. In complex 6, the Sm atom is coordinated by two Cps rings, two nitrogen atoms of 3,5-dimethylpyrazolate, and two oxygen atoms of the side-chain with a distorted tetragonal bipyramid geometry. The coordination number of the Sm atom is ten. The investigation result shows that the strong intramolecular chelating coordination and the high steric crowding result in the lower activity of 6 toward methyl methacrylate polymerization.