Synthesis and characterization of new trimetallic complexes with {Pt₂Au(μ-S) ₂} ⁿ⁺ (n=2, 3) cores containing C, N and N, N donor ligands

Abstract

Reactions of the dinuclear platinum(II) sulfide complex [Pt ₂(μ-S) ₂(PPh ₃) ₄] with a range of gold(III) dichloride complexes [AuLCl ₂] containing C, N- or N, N-cycloaurated ligands L gives a new series of dicationic adducts [Pt ₂(μ-S) ₂(PPh ₃) ₄AuL] ²⁺, isolated as their PF ₆ - salts. The complexes investigated are [Au{C₆₋H ₄(CH ₂NMe ₂)-2}Cl ₂], [Au{C ₆H ₃(CH ₂NMe ₂)-2-(OMe)-5}Cl ₂], [Au{NC ₅H ₄(CH ₂C ₆H ₄)-2}Cl ₂], [Au{NC ₅H ₄(COC ₆H ₄)-2}Cl ₂] and [Au{NC ₅H ₄(CONH)-2}Cl ₂]. An X-ray structure determination on the picolinamide-derived complex [Pt ₂(μ-S) ₂(PPh ₃) ₄Au{NC ₅H ₄(CONH)-2}](PF₆) ₂ was not of sufficiently high quality for detailed discussion, but confirmed the atom connectivity. Reactions of [Pt ₂(μ-S) ₂(PPh ₃) ₄] with [AuCl ₂(bipy)]PF ₆ (L=bipy=2,2'-bipyridine) and [AuCl ₂(phen)]Cl (L=phen=1,10-phenanthroline) gives the corresponding tricationic adducts [Pt ₂(μ-S) ₂(PPh ₃) ₄AuL] ³⁺, also isolated as their PF ₆⁻ salts. The complexes are characterised by NMR spectroscopy, electrospray mass spectrometry and microelemental analyses. Biological assay data of a selection of these new complexes towards the P388 murine leukemia cell line, as well as a range of antimicrobial tests, reveals overall low activity compared to other cycloaurated gold(III) complexes.