Oxidation of [PtIICl2(ethane-1,2-diamine-N,N'-dicarboxylic Acid)] and Ligand Ring Closure in the Platinum(IV) Oxidation State

Abstract

Oxidation of the dichloroplatinum(II) complex of the potentially tetradentate ligand ethane-1,2-diamine-N,N´-diacetic acid (H₂enda) gives rise to a variety of products. A number of these species have been crystallographically characterized. [Pt^IVCl₂(enda)] as the hemihydrate crystallizes in the monoclinic space group P2₁/a, with a 11.238(1), b 15.665(2), c 13.737(2) Å, β 109.44(1)˚, and was refined to an R value of 0.030 on 3015F. [Pt^IVCl₂(enda)] as the monohydrate crystallizes in the orthorhombic space group Pna2₁, with a 6.984(2), b 9.000(3), c 18.431(3) Å, and was refined to an R value of 0.025 on 992F. [Pt^IVCl₃(Henda)]·H₂O crystallizes in the orthorhombic space group Pbca, with a 11.741(1), b 12.851(2), c 17.133(2) Å, and was refined to an R value of 0.029 on 2015F. The major product is the ring-closed complex [Pt^IVCl₂(enda)] and if the solution is heated under reflux for 24 h, this is the only product. In contrast, reaction of cis,trans-[Pt^IVCl₂(OH)₂(ethane-1,2-diamine)] with excess acetic acid was shown not to lead to displacement of the hydroxo ligands.