N,N-Dimethylformamidinium-halometallates(I), [(DM F)2H][Me3X4] with Me3X4 = Cu3I4-, Cu3I2Br2-, Cu3I3Cl-, Ag2CuI4-, Ag3I4-, Ag3I3Br- and Ag3I3Cl- were obtained by reacting Cul or Agl with HI, HBr or HC1 in DMF. The crystal structures of the isostructural compounds (space group Pccn) are built by hydrogen-bridged DMF molecules, (DMF)2H+, as cations and a new type of polymeric anion formed by edge sharing tetrahedra triple chains. The chains consist of a double layer of halogen atoms where Cu(I)

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... d Ag(I) cations are located in tetrahedral holes. There are two kinds of halogen positions in the chains. One of them bridges two metal ions, the other is coordinated by four metal ions. In the anion chains ∞1,[Cu3I2Br2-], ∞1[Cu3I3Cl-], ∞1[Ag3I3Br-] and ∞1[Ag3I3Cl-] the lighter halogen atoms occupy the positions bridging two metal ions. The O—H—O distances range from 235-243 pm. They indicate strong hydrogen-bonding between the two DMF molecules in the (DMF)2H+ cations.