A one-dimensional bromide-bridged PtII/PtIV 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], {[PtIIPtIVBr2(C2H8N2)4](C2H4BrSO3)4·2H2O} n , crystallizes in the space group P21212. 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-[PtBr2(en)2]2+ cations (en is ethyl-enedi-amine) stacked alternately and bridged by the Br atoms. The Pt site of the [PtII/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-PtIV-Br⋯PtII⋯ chain, with PtIV-Br bond lengths of 2.453 (2) and 2.491 (3) Å, PtII⋯Br contacts of 3.069 (2) and 3.032 (3) Å, and PtIV-Br⋯PtII angles of 178.06 (13) and 177.70 (13)°. The mixed-valence state of the Pt site is expressed by the parameter δ = (PtIV-Br)/(PtII⋯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.