SYNTHESIS AND CRYSTAL-STRUCTURES OF GAMMA-TYPE OCTAMOLYBDATES COORDINATED BY CHIRAL LYSINES

The acidification of aqueous solutions containing Na2MoO4 . 2H(2)O in the presence of a chiral lysine ligand (D- and L-form) gives octamolybdates coordinating two lysine ligands, Na-2[Mo8O26(D-lysH(2))(2)]. 8H(2)O(Mo-8-D) and Na-2[Mo8O26(L-lysH(2))(2)]. 8H(2)O(Mo-8-L) (where lysH(2) is 2,6-diammoniohexanoato), respectively. These two compounds crystallize with triclinic symmetry in the space group P1, the cell parameters being a=10.782(2), b=11.241(5), c=10.027(2) Angstrom, alpha=93.21(2), beta=102.86(2), gamma=112.98(2)degrees, V=1077(1) Angstrom(3), and Z=1 for the Mo-8-D, and a=10.783(4), b=11.246(3), c=10.019(4) Angstrom, alpha=93.21(3), beta=102.75(3), gamma=112.98(2)degrees, V=1077(2) Angstrom(3), and Z=1 for Mo-8-L. The X-ray crystal structures of these two species have been solved by the MITHRIL direct method and refined to R=0.0337 and 0.0312 for Mo-8-D and -L, respectively. The chiral lysine ligands are coordinated via their carboxylate-oxygen atoms at the vacant sites on the two five-coordinate molybdenum for the centrosymmetric gamma-[Mo8O26](4-) anion to retain their configuration with a resultant formation of optically-active octamolybdate species.