Cycloplatinated ferrocenylamine-carboxylate and dithiocarbamate complexes: synthesis and aqueous properties

Abstract

Metathetical reaction of the cyclometallated ferrocenylamine complexes [Pt{FeCp(σ,η⁵-C₅H₃CHRNMe₂)}(dmso)Cl] (R = H 1 or Me 3) and [Pt₂{Fe(σ,η⁵-C₅H₃CH₂NMe₂)₂}(dmso)₂Cl₂] 2 with TlX (X = OAc or malonate), or the direct reaction with P(C₆H₄SO₃-m)₃^3– (tppms) and Et₂NCS₂^–(dedtc), gave [Pt{FeCp(σ,η⁵-C₅H₃CHRNMe₂)}(dmso)(OAc)], [{Pt[FeCp(σ,η⁵-C₅H₃CHRNMe₂)](dmso)}₂(mal)] (mal = malonate), Na₅[Pt{FeCp(σ,η⁵-C₅H₃CHRNMe₂)}(tppms)₂], [Pt{FeCp(σ,η⁵-C₅H₃CHRNMe₂)}(dedtc)] and bis-Pt analogues. These complexes were characterised by analysis, ES-MS and ¹H, ¹³C and ¹⁹⁵Pt NMR. Metathetical reaction of 1–3 with silver(I) salts generally gave ferrocenium derivatives. Substitution trans to the Pt–N or Pt–C bond is determined by the acceptor character of the co-ordinating group and this together with steric constraints limit the range of carboxylato complexes. The acetato complex [Pt{FeCp(σ,η⁵-C₅H₃CH₂NMe₂)}(dmso)(OAc)] crystallises with one molecule of H₂O and a single crystal structure indicates a hydrogen bond between a solvent H₂O and acetate ligand. Aqueous solutions of the water-soluble OAc, malonate and tppms complexes were studied by electrochemical and spectroscopic techniques. Their chemistry is regulated by pH-dependent equilibria involving aqua and hydroxo complexes and competing oxidation to the ferrocenium compound by molecular oxygen.