An electrospray mass spectrometry-directed survey of the coordination chemistry of the metalloligand [Pt₂(μ-S)₂(PPh₃)₄] with platinum(II) and palladium(II) chloride substrates: influence of metal–ligand lability on product type

Abstract

The reactivity of the metalloligand [Pt₂(μ-S)₂(PPh₃)₄] towards a wide range of platinum(II) and palladium(II) chloride complex substrates [L₂MCl₂] has been explored, using the technique of electrospray ionisation mass spectrometry to directly analyse reaction solutions. In the majority of cases, products are formed by addition of the ML₂²⁺ fragment to the {Pt₂S₂} core, giving trinuclear species [Pt₂(μ-S)₂(PPh₃)₄ML₂]²⁺. The adducts with Pt(diene) [diene=cyclo-octa-1,5-diene (cod), norbornadiene], Pd(cod), Pd(bipy) (bipy=2,2′-bipyridine), Pt(PMe₃)₂ and Pt(PTA)₂ (PTA=phosphatriaza-adamantane) moieties were synthesised and characterised on the macroscopic scale, with [Pt₂(μ-S)₂(PPh₃)₄Pt(cod)] (BF₄)₂ and [Pt₂(μ-S)₂(PPh₃)₄Pd(bipy)] (PF₆)₂ also characterised by X-ray diffraction studies. No metal scrambling was found to occur, as has been observed in some previous cases involving the related complexes [Pt₂(μ-Se)₂(PPh₃)₄] and [Pt₂(μ-S)₂(dppe)₂] (dppe=Ph₂PCH₂CH₂PPh₂). With cis-[PtCl₂(SOMe₂)₂] the species [Pt₂(μ-S)₂(PPh₃)₄PtCl(SOMe₂)]⁺ was formed, as a result of the lability of the SOMe2 ligand. With palladium(II)-phosphine systems, the observed product species is dependent on the phosphine; the bulky PPh₃ ligand in [PdCl₂(PPh₃)₂] leads primarily to the analogous known species [Pt₂(μ-S)₂(PPh₃)₄PdCl(PPh₃)]⁺, and a small amount of the metal-scrambled species [PtPd₂S₂(PPh₃)₅Cl]⁺. In contrast, [PdCl₂(PTA)₂], containing the small PTA ligand gave [Pt₂(μ-S)₂(PPh₃)₄Pd(PTA)₂]²⁺. A survey of the reactions of [Pt₂(μ-S)₂(PPh₃)₄] with platinum(II) and palladium(II) dichloride substrates [L₂MCl₂] has been carried out using electrospray ionisation mass spectrometry; the dominant theme is the formation of dicationic species [Pt₂(μ-S)₂(PPh₃)₄ML₂]²⁺, but with some exceptions, which are discussed. The complexes [Pt₂(μ-S)₂(PPh₃)₄Pt(cod)](BF₄)₂ (cod=cyclo-octa-1,5-diene) and [Pt₂(μ-S)₂(PPh₃)₄Pd(bipy)] (PF₆)₂(bipy=2,2′-bipyridine) were characterised by X-ray diffraction studies.