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

The title salt, catena-poly[[[bis­(ethyl­enedi­amine)­platinum(II)]-μ-bromido-[bis(ethyl­enedi­amine)­platinum(IV)]-μ-bromido] tetra­kis­(2-bromo­ethane­sulfon­ate) 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 octa­hedral trans-[PtBr(2)(en)(2)](2+) cations (en is ethyl­enedi­amine) 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) Å, Pt(II)⋯Br contacts of 3.069 (2) and 3.032 (3) Å, 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 mol­ecules of crystallization, stabilize the cationic columnar structure.