Formation of negative ions of monosubstituted group VIB pentacarbonyls during fast atom bombardment mass spectrometry

Abstract

AbstractThe first negative‐ion fast atom bombardment mass spectra of a related series of monosubstituted Group VIB transition metal pentacarbonyls, M(CO)5L (M = Cr), Mo or W and L = P(Ph)3, As(Ph)3 or Sb(PH)3), have been obtained. Instead of molecular ion radicals, pseudomolecular adduct ions, [M + H]− and [M + 15]−, were detected, with the hydride species being much more abundant. High‐resolution measurements and comparison of observed isotope clusters with computer‐generated theoretical isotope patterns confirmed that ionization occurred by several mechanisms, including electron capture, charge dissociation and formation of adducts with charged species. Fragmentation consisted primarily of elimination of neutral ligands, i.e. ([MH ‐ L]−, [MH ‐ CO]−, [MH ‐ 2CO]−, etc. B/E and constant neutral loss linked scanning with collisional activation were used to confirm fragmentation pathways and characterize the site of hydride attachment on the transition metal complex. The information obtained demonstrates the utility of fast atom bombardment mass Spectrometry in the analysis of metal carbonyls.