Abstract: By using the reaction of Cp₃Ln(Cp = C₅H₅; Ln = Sm, Dy, Ho) with 8-hydroxyquinoline (HL)(1:1 molar ratio) in tetrahydrofuran at room temperature, three new organoianthanide complexes with the general formula Cp₂LnL( Ln = Sm, Dy, Ho) were synthesized.All the complexes were characterized by elementary analysis, IR, XPS, MSspectra and cryoscopic method for molecular weight determination.The results of elemental analyses confirmed to the formula Cp₂LnL.The IRspectra show the characteristic absorptions of η5-Cp group at about 3100, 1440, 1010, 780 and 250 cm^-1, and 8-hydroxyquinolinoiato metal chelates near 560 cm^-1.XPSdata revealed that the N,, binding energy of Lligand in each complex is higher than that of sodium salt of 8-hydroxyquinoline, which indicates that Liigand coordinates to metal through nitrogen and oxygen atoms to form an intramolecular five-membered chelating ring.Molecular weight determination by cryoscopic method in benzene suggests each complex exists as a dimer with oxygen atoms of Lligands as bridging atoms.MSspectra show only the monorneric molecular ion peaks of the complexes, which may indicate that upon heating, the dimeric complexes easily dissociate into a monomer.Due to the effect of chelating coordination, the title complexes have higher stability compared to the corresponding Cp₂LnCl and Cp₃Ln complexes.The thermal stabilities of the complexes were studied and compared eath other.Complex Cp₂SmLis thermally unstable and tends to decompose into Cp₃Sm and SmL₃ at above 180℃.

Key words: Lanthanide complexes, 8-hydroxyquinoline, Cyciopentadienyl, Synthesis, Thermal stability