A one-dimensional bromide-bridged Pt(II)/Pt(IV) mixed-valence complex with a 2-bromo-ethane-sulfonate counter-ion.

The title salt, catena-poly[[[bis-(ethyl-enedi-amine)-platinum(II)]-μ-bromido-[bis(ethyl-enedi-amine)-platinum(IV)]-μ-bromido] tetra-kis-(2-bromo-ethane-sulfon-ate) dihydrate], {[Pt(II)Pt(IV)Br(2)(C(2)H(8)N(2))(4)](C(2)H(4)BrSO(3))(4)·2H(2)O} (n) , crystallizes in the space group P2(1)2(1)2. It has a linear chain structure extending parallel to the c axis, composed of square-planar [Pt(en)(2)](2+) and elongated octa-hedral trans-[PtBr(2)(en)(2)](2+) cations (en is ethyl-enedi-amine) stacked alternately and bridged by the Br atoms. The Pt site of the [Pt(II/IV)(en)(2)] unit is located on a general position. The Br site, which is also located on a general position, is equally disordered over two positions. The Pt and Br atoms form a slight zigzag ⋯Br-Pt(IV)-Br⋯Pt(II)⋯ chain, with Pt(IV)-Br bond lengths of 2.453†(2) and 2.491†(3)†à , Pt(II)⋯Br contacts of 3.069†(2) and 3.032†(3)†à , and Pt(IV)-Br⋯Pt(II) angles of 178.06†(13) and 177.70†(13)°. The mixed-valence state of the Pt site is expressed by the parameter δ = (Pt(IV)-Br)/(Pt(II)⋯Br), with values of 0.799 and 0.822 for the two independent Br atoms. In the crystal, N-H⋯O and O-H⋯O hydrogen bonds between the amine groups of the Pt complex chains, the sulfonate groups and water mol-ecules of crystallization, stabilize the cationic columnar structure.