Clustering of palladium(II) chloride in acetonitrile solution investigated by electrospray mass spectrometry

Solutions of palladium chloride in acetonitrile are investigated by means of electrospray ionization mass spectrometry (ESI-MS). In contrast to several other metal salts previously investigated using ESI-MS, PdCl2 has a pronounced tendency for aggregation to yield [PdmCl2m−1(CH3CN)n]+ clusters in the positive ion mode and [PdmCl2m+1]− clusters when the negative ions are sampled, respectively. The observation of these oligomers parallels polymeric structures of PdCl2 in the solid phase. The positive ions are most abundant for m = 2 and generally associated with several molecules of the solvent, whereas many different cluster sizes occur for the anions which generally do not appear as solvent associates. Parallel conductivity measurements in the condensed phase lend support to a pronounced tendency for aggregation of PdCl2 in acetonitrile solution.

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► Sampling of solution properties via ESI-MS.
► Pronounced aggregation of PdCl2 in acetonitrile solution.
► Partial reduction of anionic clusters to palladium(I).
► Implications for palladium catalysis.