The preparation and crystal and molecular structure of the complex cis-PtCl 2(razoxane)

Abstract

Treatment of K 2[PtCl 4] with the anti-cancer drug razoxane (3,5-dioxopiperazin-1-yl-propane) in aqueous HCl solution gave the water-insoluble complex cis-PtCl 2(razoxane), which is the first metal complex of razoxane to have been isolated. The crystal and molecular structure of the complex confirms that razoxane is present as a bidentate ligand, Pt-N = 2.095(11) and 2.080(9) Å, and was not hydrolysed during complex formation as was previously observed in the presence of other metal ions. This is also one of the few examples in which platinum is bonded to a ligand via tertiary nitrogen atoms only. The presence in the complex of two cis chloride ligands, Pt-Cl = 2.299(4) and 2.277(3) Å, and square planar geometry around the metal ion is also confirmed. Intermolecular hydrogen bonding between an imide oxygen atom of each molecule and an imide NH group of another results in a sheet-like ‘zig-zag’ structure. Crystal data for cis-PtCl 2(razoxane): monoclinic, space group P2 1/ c, a = 9.165(2), b = 16.573(3), c = 10.984(2) Å, β = 114.60(3)°, Z = 4, R = 0.0341, R w = 0.0385.