Fragmentation of transition metal carbonyl cluster anions: Structural insights from mass spectrometry

The anionic clusters HOs5-(Co)(15), PtRu5C(CO)(15), Os10C-(CO)(24), Os-17(CO)(36), Os-20(CO)(40) [Co6C(CO)15]2-, Pt3Ru10C2-(CO)(32) and Pd6Ru6(CO)(24) have been analysed by energy-dependent electrospray ionisation mass spectrometry (EDESI-MS). Three main features have emerged. Firstly, carbonyl ligands are fragmented from clusters with compact metal cores in an orderly fashion, with each of the ions generated by CO loss having approximately equal intensity. Secondly. electron autodetachment takes place in multiply charged anionic clusters. but only after elimination of a large proportion of their carbonyl ligands. Thirdly, clusters with open metal cores do not undergo CO loss in an orderly fashion. but certain peaks are considerably less intense. The appearance of these low-intensity peaks is believed to signify polyhedral core rearrangements, with open clusters folding to form more compact geometries. In some cases. the gas-phase transformations observed by EDESI-MS mirror those that are known to take place in solution.