{Zn₆[MeN(CH₂CO₂)(CH₂PO₃)]₆(Zn)}^4- Anion:  The First Example of the Oxo-Bridged Zn₆ Octahedron with a Centered Zn(II) Cation

Hydrothermal reactions of N-(phosphonomethyl)-N-methylglycine, MeN(CH₂CO₂H)(CH₂PO₃H₂) (H₃L), with zinc(II) acetate resulted in the formation of a novel zinc carboxylate−phosphonate, {Zn₆L₆(Zn)}{Zn(H₂O)₆}₂·22H₂O (1). The structure of 1 contains a heptanuclear zinc phosphonate cluster anion, {Zn₆L₆(Zn)}^4-, in which seven zinc(II) cations form an unusual Zn₆(Zn) centered octahedron with six of its Zn₃ triangle faces each further capped by a phosphonate group. The Zn(II) cations of the Zn₆ octahedron are five-coordinated whereas the centered Zn(II) cation is octahedrally coordinated. Packing of these cluster anions creates micropores occupied by the hydrated zinc(II) cations as well as lattice water molecules. The structural skeleton of 1 is retained after the removal of the lattice water molecules.