ELECTROSPRAY MASS SPECTROMETRY APPLIED TO METAL CLUSTER CHEMISTRY

William Henderson,^a Brian K. Nicholson,^a J. Scott McIndoe,^a Paul J. Dyson,^b Thomas Lover,^c Graham A. Bowmaker^c and Ralph P. Cooney^c

^aDepartment of Chemistry, University of Waikato, Hamilton, New Zealand
^bDepartment of Chemistry, Imperial College of Science, Technology & Medicine, London, U.K.
^cDepartment of Chemistry, University of Auckland, Auckland, New Zealand

Neutral binary metal carbonyls typically yield non-existent ESMS spectra under standard operating conditions (MeCN-H₂O mobile phase, range of cone voltages). However, strong [M + OR]^- ions are readily obtained by recording spectra in an alcohol ROH, containing a small amount of added sodium alkoxide NaOR; this ionisation technique is applicable to the vast majority of metal carbonyls. Certain metal carbonyl clusters [e.g. Ru₃(CO)₁₂] also yield [M + Ag(solvent)]⁺ ions with added Ag⁺, thus providing a useful alternative ionisation pathway. The neutral metal carbonyls, once ionised by one of the above techniques, undergo the expected cone voltage-induced loss of CO ligands. The general applicability of these new ionisation techniques will be illustrated.

Metal-chalcogenide-thiolate clusters are attracting much interest for their potential as precursors for the preparation of metal-chalcogenide phases (e.g. ZnSe, CdS) with monodisperse particle sizes. Clusters of the type [M₄(SPh)₁₀]^2- (M = Zn, Cd), [S₄M₁₀(SPh)₁₆]^4- (M = Zn, Cd), [Se₄Cd₁₀(SPh)₁₆]^4-, and [S₄Cd₁₇(SPh)₂₈]^2- all display strong negative ion ESMS spectra, and all fragment ions have been fully assigned. ESMS also provides a convenient method for investigating exchange processes involving these clusters, including metal, chalcogenide, and thiolate exchange.