Studies on organolanthanide complexes XLVII. Syntheses of bis(2-methoxyethylcyclopentadienyl)lanthanide tetrahydroborates (Ln = La, Pr, Nd, Sm or Gd); Crystal structures of bis(2-methoxyethylcyclopentadienyl) praseodymium and neodymium tetrahydroborates

Abstract

Five new complexes, bis(2-methoxyethylcyclopentadienyl) lanthanide tetrahydroborates (Ln = La ( 1), Pr ( 2), Nd ( 3), Sm ( 4) or Gd ( 5)) have been synthesized with good yields by the reaction of bis (2-methoxyethylcyclopentadienyl)lanthanide chlorides with sodium borohydride in THF at room temperature. These complexes have been characterized by elemental analyses, MS, 1H NMR and IR spectra. The X-ray structure analyses of 2 and 3 show both to be orthorhombic, with space group P2 12 12 1, a 11.081(3)A˚, b = 13.145(5)A˚, c = 12.080(3)A˚, D calc = 1.518 g cm −3 and Z = 4 for 2, and space group P na2 1, a = 12.753(2)A˚, b = 11.207(2)A˚, c = 12 .042(2)A˚, D cal = 1.565 g cm −3 and Z = 4 for 3. The structures were solved from 2982 observed reflections with F o ⩾= 4σ (F o) to a final R factor of 0.0610 for 3. The molecular structures show that they are monomers, and intramolecular coordination bonds between lanthanide metal and oxygen atom on ligand in the above tetrahydroborate complexes exist. The average Pr-O and Nd-O bond lengths are 2.605A˚and 2.560A˚respectively. The X-ray crystal structures also reveal that the Pr … B distance is 2.757(18)A˚and the Nd … B distance is 2.664(25)A˚and suggest the tridentate mode of BH 4 − bonding.