Reactions of the thiosulfate ligand (as sodium thiosulfate, Na2S2O3·5H2O) with phosphine complexes of the group 10 metals Ni(II), Pd(II) and Pt(II) resulted in five neutral thiosulfate complexes, [Ni(S2O3)(dppe)] (dppe = Ph2PCH2CH2PPh2), [Pd(S2O3)(dppe)], [Pd(S2O3)(dppf)] (dppf = Fe(C5H4PPh2)2), [Pd(S2O3)(PPh3)2] and [Pt(S2O3)(PPh3)2]. X-ray structure determinations of [Pd(S2O3)(dppf)], [Pd(S2O3)(PPh3)2] and [Pt(S2O3)(PPh3)2] confirmed that thiosulfate ligand coordinates as a bidentate chelating ligand via both sulfur and oxygen donor atoms. In addition, reactions of the thiosulfate ligand with dinuclear chloride-bridged cyclopalladated complexes gave four mononuclear anionic complexes [Pd(S2O3)(damp)]− (damp = N,N-dimethylbenzylamino, (CH3)2NCH2C6H4), [Pd(S2O3)(ptpy)]− (ptpy = p-tolylpyridyl), ]Pd(S2O3)(bzpy)]− (bzpy = 2-benzylpyridyl) and [Pd(S2O3))pap)]− (pap = 2-(phenylazo)phenyl). The structure of (Ph3PCH2Ph)[Pd(S2O3)(pap)] by X-ray crystallography revealed the ability of thiosulfate ligand to cleave the bridging chloride ligand on the starting complexes by acting as an S,O-donor chelating ligand. An ESI mass spectrometric investigation showed that the coordinated thiosulfate ligand undergoes fragmentation at elevated capillary exit voltages.