Stable mixed-valence diphenylphosphanido bridged platinum(ii)-platinum(iv) complexes

The reaction between [NnBu4][(C6F5)2PtII(μ-PPh2)2PtIV(C^N)(I)2] (C^N = κ2-N,C-benzoquinolinate, 1) and (i) bidentate S^S, N^S and O^O anionic ligands or (ii) monodentate S- N- or O-based anionic ligands was studied in order to investigate the factors that may guarantee the stability of Pt(ii),Pt(iv) mixed-valence dinuclear phosphanido complexes. While reactions of 1 with S^S or N^S ligands afforded stable Pt(ii),Pt(iv) species of general formula [(C6F5)2PtII(μ-PPh2)2PtIV(C^N)(L^S)]x- [(L^S)(x-1) = 2-mercaptopyrimidinate (pymS-), 2-mercaptopyridinate (pyS-), dimethyldithiocarbamate (Me2NCS2-), ethyl xanthogenate (EtOCS2-) and 1,2-benzenedithiolate (PhS22-)], the reaction of 1 with the O^O ligand sodium acetylacetonate gave several products, and no pure Pt(ii),Pt(iv) complex could be isolated. The reaction of monodentate ligands such as PhS-, OH- or N3- with 1 led to a stable Pt(ii),Pt(iv) complex only in the case of N3-. The reaction with OH- afforded the Pt(ii),Pt(ii) complex [(C6F5)2PtII(μ-PPh2)(κ2-O,P-μ-O-PPh2)PtII(C^N)]- (8) deriving from reductive coupling of a diphenylphosphanide and an O-donor ligand coordinated to the Pt(iv) centre, while the reaction with PhS- produced the unstable Pt(ii),Pt(iv) complex [NnBu4][(C6F5)2PtII(μ-PPh2)2PtIV(C^N)(PhS)2] (11) that evolved in solution to the Pt(ii),Pt(ii) species [NnBu4][(C6F5)2PtII(μ-PPh2)2PtII(C^N)] (9) by elimination of diphenyldisulfide. Thus, the stability of mixed valence Pt(ii),Pt(iv) phosphanide complexes is affected by several concurrent factors, including the chelating effect of the ligands and the type of ligating atoms.

Efficient Sustainable Tool for Monitoring Chemical Reactions and Structure Determination in Ionic Liquids by ESI-MS

An easy and convenient procedure is described for monitoring chemical reactions and characterization of compounds dissolved in ionic liquids using the well-known tandem mass spectrometry (MS/MS) technique. Generation of wastes was avoided by utilizing an easy procedure for analysis of ionic liquid systems without preliminary isolation and purification. The described procedure also decreased the risk of plausible contamination and damage of the ESI-MS hardware and increased sensitivity and accuracy of the measurements. ESI-MS detection in MS/MS mode was shown to be efficient in ionic liquids systems for structural and mechanistic studies, which are rather difficult otherwise. The developed ESI-MS/MS approach was applied to study samples corresponding to peptide systems in ionic liquids and to platform chemical directed biomass conversion in ionic liquids.