Fast Atom Bombardment Mass Spectrometry of Arene-Chromium, Complexes: Cr(q~~-c~Ph~)~, Cr(q6-PhPh(Cr(C0)3))2 and Fe{~-csH~-~f-

The fast atom bombardment mass spectra of several high molecular weight q-arenechromium complexes have been measured and analysed. Interesting features include the observation of loss of CzPh2 from [Cr(C6Ph6)zIf to give [Cr(CloPhlo)]+ as the base peak, which appears to be derived from pentaphenylcyclopentadiene; the ready loss of Cr(C0)3 moieties from complexes containing this group; and the formation of ions containing CrFe groups in the spectra of the ferrocene derivatives.