Template-directed synthesis of three metal oxalates via 4-connected building units

Abstract

Three novel compounds, [Co(en)3]2[Zr2(C2O4)7]·2H2O(HNU-2, en=ethylenediamine), [Co(NH3)6]· [Ce(C2O4)3(H2O)]·H2O(HNU-3) and [Co(dien)2][Gd(C2O4)3]·0.75H2O(HNU-4, dien=dethylenetriamine) were hydrothermal synthesized based on the templates of [Co(en)3]Cl3, [Co(NH3)6]Cl3 and [Co(dien)2]Cl3, respectively. The Zr4+, Ce3+ and Gd3+ cations are all coordinated by four oxalates to form [M(C2O4)4(H2O) n ] m−(M=Zr, Ce or Gd; n=0 or 1; m=4 or 5), which are similar to [In(C2O4)4]5− in NKB-1, and can be regarded as 4-connected building units. The [M(C2O4)4(H2O) n ] m− units are connected via sharing the bis-bidentate bridging oxalate ligands to form binuclears in HNU-2 and 1D “zigzag” chains in HNU-3 and HNU-4. It is suggested that these compounds could be used as molecular building units to design 3D open frameworks with zeolite topologies.