Towards the water solubilization of [Pt2(μ-S)2(PPh3)4] derivatives by polyether functionalization – a synthetic and mass spectrometric investigation

Synthetic methods have been developed to append polyether chains onto the nucleophilic platinum(II) sulfide complex [Pt2(μ-S)2(PPh3)4] through alkylation reactions of a sulfide ligand. Reaction of [Pt2(μ-S)2(PPh3)4] with Br(CH2)2NHC(O)NH(CH2)2OMe gave the monoalkylated model complex [Pt2(μ-S){μ-S(CH2)2NHC(O)NH(CH2)2OMe}(PPh3)4]+, isolated as its salt. Extension of this methodology to the polyether-derived alkylating agent Br(CH2)2NHC(O)NHCHMeCH2(OCHMeCH2)nOCH2CH2OMe derived from the polyether amine Jeffamine® M600 gave the cation [Pt2(μ-S){μ-S(CH2)2NHC(O)NHCHMeCH2(OCHMeCH2)nOCH2CH2OMe}(PPh3)4]+, isolated as its salt and characterized by ESI MS and 31P{1H} NMR spectroscopy. Reaction of [Pt2(μ-S)2(PPh3)4] with the chloro-PEG Me(OCH2CH2)nCl (derived from MeOPEG 350) in the presence of NaBr in refluxing methanol proceeded slowly, giving [Pt2(μ-S){μ-S(CH2CH2O)nMe}(PPh3)4]+, isolated as its salt. The aqueous solubility of a selection of compounds was determined.