Comparison of electron impact, desorption chemical ionization, field desorption, and fast atom bombardment mass spectra of nine monosubstituted Group VI metal carbonyls

Nine monosubstituted group VI metal pentacarbonyls of the type M(CO)/sub 5/L (where M = Cr, Mo, or W; and L = P(C/sub 6/H/sub 5/)/sub 3/, As(C/sub 6/H/sub 5/)/sub 3/, or Sb(C/sub 6/H/sub 5/)/sub 3/) were synthesized and purified by recrystallization so that they contained no unbound ligands, excess reagents, or other contaminants as measured by high-performance liquid chromatography. Positive ion mass spectra were obtained by electron impact (EI), desorption chemical ionization (DCI), field desorption (FD), and fast atom bombardment (FAB) mass spectrometry. B/E linked scanning was used to confirm the fragmentation pathway in FAB mass spectra. While all four ionization methods formed molecular ions, M/sup +/, the desorption ionization methods tended to produce more abundant molecular ions than EI. FD, for instance, formed molecular ions without any fragmentation. The most abundant fragment ions of the ligand (L) were observed with DCI. FAB spectra contained abundant molecular ions and extensive structural information in ion fragments.