Synthesis and Crystal Structures of <i>γ</i>-Type Octamolybdates Coordinated by Chiral Lysines

Abstract

Abstract The acidification of aqueous solutions containing Na2MoO4·2H2O in the presence of a chiral lysine ligand (d- and l-form) gives octamolybdates coordinating two lysine ligands, Na2[Mo8O26(d-lysH2)2]·8H2O (Mo8-d) and Na2[Mo8O26(l-lysH2)2]·8H2O (Mo8-l) (where lysH2 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) Å, α = 93.21(2), β = 102.86(2), γ = 112.98(2)°, V = 1077(1) Å3, and Z = 1 for the Mo8-d, and a = 10.783(4), b = 11.246(3), c = 10.019(4) Å, α = 93.21(3), β = 102.75(3), γ = 112.98(2)°, V = 1077(2) Å3, and Z = 1 for Mo8-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 Mo8-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 γ-[Mo8O26]4− anion to retain their configuration with a resultant formation of optically-active octamolybdate species.