Complexes of halide ions with diiodoacetylene. The crystal structures of PPh(4)[X(I-C C-I)(2)] with X=Cl, Br, I

The complexes PPh(4)[X(I-C=C-I)(2)] with X = Cl (1), Br (2), and I (3) have been prepared from the phosphonium salts PPh(4)X and I-C=C-I in dichloromethane solutions. 1-3 form colourless crystals, which according to crystal structure analysis crystallize isotypically in the space group P (4) over bar 2(1)m with two formula units per unit cell. The diiodacetylenes are coordinated by the halide ions X(-) in a distorted tetragonal fashion, the I-C=C-I molecules being in mu(2)-bridging function. Thus, a polymeric anionic network [X(I-C=C-I)(2)](n-)(n) with a layered structure results.