Structural variations in rare earth benzoate complexes Part II. Yttrium and terbium

Abstract

A series of yttrium and terbium benzoate complexes have been prepared and structurally characterised as DMF or DMSO solvates, often also hydrated. The structures of these complexes vary considerably as a function of the steric bulk of the ligands and the degree of solvation. The smaller rare-earth elements, yttrium and terbium, are of comparable size and are observed to behave in a similar manner with several isomorphous complexes being formed and with the majority being dimeric. Six (μ-η¹∶η¹)₂ bridged dimeric complexes of the form [Ln(O₂CR)₆(solv)₂(H₂O)₂] (O₂CR = benzoate, 3- and 4-methylbenzoate or 4-methoxybenzoate, solv = DMF or DMSO) have similar structures, despite a change in the ligand or the solvent of crystallisation. A different dimeric product containing four, rather than two, bridging ligands between the two metal atoms has been obtained with 4-nitrobenzoate, [Tb(4-NO₂BA)₃(DMF)(H₂O)]₂·4DMF, 9. A variety of polymeric products were synthesised that differ significantly from each other with a variety of benzoate binding modes and interesting intra- and inter-molecular hydrogen bonding motifs involving solvent molecules. Of particular interest are the solvent-free polymer [Y(2-MeBA)₃]_∞3, the yttrium polymer of 3-nitrobenzoate [{Y(3-NO₂BA)₃(DMSO)}{Y(3-NO₂BA)₃(H₂O)₂}] 8, containing two unique metal atoms in the repeating unit, and two polymers (8 and 10, {[Ln(4-NO₂BA)₃(DMSO)(H₂O)₂]·DMSO}_∞ (Ln = Tb (10b), Y (10a))) that incorporate η¹ benzoate ligands.