AMINO ACID-LANTHANIDE INTERACTIONS. CRYSTAL STRUCTURES OF LANTHANIDE COMPLEXES OF a- AMINO ISOBUTYRIC ACID (Aib), (La,(Aib),(H,O),) (ClO& AND (Pr,(Aib),(H,O),)C1, Hz0

The structures of (La2(Aib)4(H20),)(C104)6 (1) and (Pr2(Aib)4(H20)8)C16* H20 (2) have been determined by X-ray crystallography and show that the two lanthanide cations are bridged by carboxyl groups of four Aib molecules and are surrounded by four oxygen atoms from water molecules thus making the coordination number 8. The geometry around the lanthanum ion in 1 is a distorted bicapped trigonal prism whereas the praseo- dymium ion in 2 exhibits a square antiprismatic arrangement of the ligands. Coordination mode of Aib is compared with that in other metal complexes.