AMINO ACID-LANTHANIDE INTERACTIONS - CRYSTAL-STRUCTURES OF LANTHANIDECOMPLEXES OF ALPHA-AMINO ISOBUTYRIC ACID (AIB), [LA2(AIB)4(H2O)8](CLO4)6 AND [PR2(AIB)4(H2O)8]CL6.H2O

The structures of [La2(Aib)4(H2O)8](ClO4)6 (1) and [Pr2(Aib)4(H2O)8]Cl 6.H2O (2) have been determined by X-ray crystallography and show that the two lanthanide cations are bridged by carboxyl groups fo four Aib molecules and are surrounded by four oxygen atoms from water molecules thus making the coordination number 8. The geometry around the lantha num ion in 1 is a distorted bicapped trigonal prism whereas the praseo dymium ion in 2 exhibits a square antiprismatic arrangement of the lig ands. Coordination mode of Aib is compared with that in other metal co mplexes.