Bis(2-methoxyethylcyclopentadienyl)yttrium and -ytterbium tetrahydroborates have been synthesized in good yields by the reaction of bis(2-methoxyethylcyclopentadienyl)lanthanide chlorides with sodium borohydride in THF at room temperature The title complexes were characterized by elemental analyses, MS, 1H NMR and IR spectra. The crystal structures of the title compounds have been determine by x-ray diffraction. The x-ray structures and IR reveal the bidentate yttrium and ytterbium tetrahydroborate complexes with the intramol. coordination bonds between lanthanide metal and ligand oxygen atoms.

Key words: CRYSTAL STRUCTURE DETERMINATION, INFRARED SPECTROPHOTOMETRY, X-RAY DIFFRACTION ANALYSIS, CYCLOPENTADIENE P, PROTON MAGNETIC RESONANCE SPECTROMETRY, YTTRIUM COMPLEX, YTTERBIUM COMPLEX, BORANES