Ion chemistry of a series of cluster compounds with Mo3Q4 and Mo3M′Q4 (Q = S, Se; M′ = Cu, Co, Ni) cores containing 1,2 diphosphanes as ancillary ligands: New insights on the gas-phase stability from electrospray tandem mass spectrometry

Electrospray ionization (ESI) and tandem mass spectrometry for the family of trinuclear [Mo3Q4(dmpe)3Cl3]+ and tetranuclear [Mo3(M′L)Q4(dmpe)3Cl3]0,+ (dmpe = 1,2-bis(dimethylphosphanyl)ethane); (Q = S, Se; M′ = Cu, Co, Ni; L = Cl, CO) complexes have been investigated. Release of two diphosphane molecules appears to be a common fragmentation channel for the trinuclear compounds while fragmentation paths in the tetranuclear complexes are mainly determined by the nature of the ligand coordinated to the heterometal M′, namely CO, Cl. Tetranuclear complexes with M′CO start evolving the CO ligand followed by two diphosphane molecules. For compounds incorporating the M′Cl fragment, the losses of the diphosphane ligands comes together with the breaking of the cuboidal Mo3M′Q4 unit to afford trinuclear Mo3Q4 species. In the latter case, neutral losses corresponding to M′Cl and M′Cl2 fragments are observed for M′ = Cu and Co, respectively, whereas both neutral fragments are simultaneously released for M′ = Ni. Energy-dependent collision induced dissociation (CID) experiments have been used to extract information about the relative stability of these cuboidal compounds in the gas-phase. On the basis of the relative intensities of the molecular precursor ions and the fragmentations peaks, a qualitative analysis of the M′–CO, Mo-diphosphane and Mo3–M′ bond energetics is discussed.