Chiral and achiral platinum(II) complexes for potential use as chemotherapeutic agents: crystal and molecular structures of cis-[Pt(L1)2] and [Pt(L1)Cl(MPSO)] [HL1 = N,N-diethyl-N ′-benzoylthiourea

Abstract

The synthesis and characterisation of platinum(II) complexes, with the general formula [Pt(acylthioureato)Cl(RR′SO)], is reported. These complexes are readily formed by the reaction of [PtCl2(RR′SO)2] with the acylthiourea ligands, N,N-di(2-hydroxyethyl)-N′-benzoylthiourea (HL), N,N-diethyl-N′-benzoylthiourea (HL1) and N,N-adipoylbis(N′,N′-diethylthiourea) (H2L2) in the presence of sodium acetate. Variation of the sulfoxide ligand (RR′SO) enables preparation of achiral complexes when RR′SO is dimethylsulfoxide (DMSO) or methylphenylsulfoxide (MPSO), and chiral complexes when use is made of the chiral sulfoxides, such as (R)-methyl(p-tolyl)sulfoxide and (S)-methyl(p-tolyl)sulfoxide. The reaction also yields, as a minor product, the corresponding cis-bis(acylthioureato)platinum(II) complexes, which can be removed by chromatography. The molecular structures of the two products, [Pt(L1)Cl(MPSO)] and cis-[Pt(L1)2], were determined by X-ray crystallography. The sulfoxide of [Pt(L1)Cl(MPSO)] is sulfur bound, as expected, and cis to the sulfur atom of the acylthioureato ligand. All bond lengths and bond angles around the square planar platinum are normal, with the Pt–S bond trans to Cl being 2.257(4) A and the Pt–S bond trans to O 2.192(3) A in length. The Pt–O and Pt–Cl bonds are 2.016(9) and 2.334(3) A, respectively, and are within the expected ranges. Similarly, the bond lengths and bond angles around the coordination plane of cis-[Pt(L1)2] compare well with related complexes.