Characterisation of cationic co-ordination complexes using field desorption mass spectrometry

Abstract

Field desorption (f.d.) mass spectrometry has been shown to provide a useful method for the characterisation of involatile monocationic co-ordination complexes. With square-planar compounds of the type [Pd(dien)X]X [X = Cl or Br; dien = iminobis (ethyleneamine)], [Pd(Et₄dien)X]X [X = l or NCS; Et₄dien = iminobis(ethylenediethylamine)], and a variety of octahedral complexes of the type cis-[Co(en)₂X₂]Y (X = NO₂, Y = l; or X = NCS, Y = NO₃; en = 1,2-diaminoethane), [Co(en)₂(sal)][NO₃](sal = salicylate), and cis-[Ru(en)₂Cl₂]Cl the base peak corresponds to the molecular ion [M]˙⁺ for the cation and no fragmentation is observed. However, for the related complexes trans-[Co(en)₂X₂]X (X = Cl or Br) and trans-[Co{(–)pn}₂Cl₂]Cl (pn = 1,2-diaminopropane) no [M]˙⁺ peaks are observed, and fragment ions associated with ligand loss are seen. Useful f.d. mass spectra can also be obtained with some di- and tri-cationic co-ordination complexes, but the results are less reproducible and sometimes difficult to rationalise.