ELECTROSPRAY MASS-SPECTROMETRY OF THIOPHENOLATE-CAPPED CLUSTERS OF CDS, CDSE, AND ZNS AND OF CADMIUM AND ZINC THIOPHENOLATE COMPLEXES - OBSERVATION OF FRAGMENTATION AND METAL, CHALCOGENIDE, AND LIGAND-EXCHANGEPROCESSES

Electrospray mass spectrometry provides a rapid, convenient technique for characterizing and studying the chemistry of anionic metal sulfide thiolate clusters. Negative-ion electrospray mass spectra have been r ecorded for the thiophenolate-capped clusters [Me4N](4)[E4Cd10(SPh)(16 )] (E = S, Se), [Me4N](4)[S4Zn10(SPh)(16)], and [Me4N](2)[S-4-Cd-17(SP h)(28)] and of the metal thiophenolate complexes [Me4N](2)[M(SPh)(4)], [Me4N](2)[M-4(SPh)(10)] (M = Cd, Zn), and [Et4N](2)[Cd4X4(SPh)(6)] (X = Cl, Br, I). The exchanges of M, E, and X which occur in various mix tures of these clusters and complexes and the fragmentation processes have been investigated. In the clusters the M-E bonds involving the su lfide or selenide core remain intact during the observed fragmentation at low cone voltages. At high cone voltages, monoions are ultimately formed by loss of charged species and neutral M(SPh)(2), resulting in almost complete removal of the SPh- ligands from the cluster core. Fra gmentation of the ME core unit itself occurs only at very high voltage s. The exchange of X in [Et4N](2)[Cd4X4(SPh)(6)] (X = Br, I) gives pea ks due to the ions [Cd4InBrm(SPh)(10-(n+m))](2-) (n + m = 0-4) and fra gment ions with mixed ligands. The nature of the detected species sugg ests that the halides only exist as terminal ligands. The exchange of M in [Me4N](2)[M-4-(SPh)(10)] and [Me4N](4)[S4M10(SPh)(16)] results in the mixed-metal complexes [Cd4-nZnn(SPh)(10)](2-) (n = 0-4) and the m ixed-metal clusters [S4Cd10-nZnn(SPh)(16)](4-) (n = 0-10). The exchang e follows random statistics in [M-4(SPh)(10)](2-) but is biased toward equilibrium association of the same metal in [S4M10(SPh)(16)](4-). Th e rates of exchange within the different structural elements of [S4M10 (SPh)(16)](4-) and [S4M17(SPh)(28)](2-) decrease for the atoms located toward the center of the clusters.