MASS SPECTRA OF METAL CHELATES .I. SUBSTITUENT EFFECTS ON IONIZATION POTENTIALS AND FRAGMENTATION PATTERNS OF SOME 1-METHYL-3-ALKYL-1,3-DIONE-COPPER(2) CHELATES

The mass spectra of a series of bis(β-ketoenolate) complexes of copper(II), as well as bis(2,2-dimethyl-3,5-hexanedionato)zinc(II) and bis(2,2-dimethyl-3,5-hexanedionato)magnesium(II), show the same preferential fragmentation pattern, the most striking characteristic being the stepwise removal of the alkyl substituents. The populations of the species arising from this fragmentation process vary and can be rationalized on the basis of the electronic effects of the alkyl substituents; the ionization potentials of the copper chelates also reflect this trend. In all of these spectra a reaction of the chelate within the mass spectrometer, apparently a substitution of Cu by Fe, is observed under a variety of conditions. © 1969, American Chemical Society. All rights reserved.