BIMOLECULAR GAS-PHASE REACTIONS OF D-BLOCK TRANSITION-METAL CATIONS WITH DIMETHYL PEROXIDE - TRENDS ACROSS THE PERIODIC-TABLE

The bimolecular gas-phase reactions of d-block transition-metal cation s M(+) with dimethyl peroxide were screened by means of Fourier transf orm ion cyclotron resonance mass spectrometry. The rich chemistry can be classified into four types of reactions: i) Oxygen-atom transfer to generate MO(+), ii) elimination of radicals, mostly CH3O., iii) intra molecular redox reaction of dimethyl peroxide to form CH3OH, CH2O and CO, and iv) charge transfer from the metal cation to produce CH3OOCH3. Some general trends became apparent from this study. For example, th e ''early'' transition metals almost exclusively induce oxygen transfe r to generate MO(+), in line with the notoriously high oxophilicities of these metals, and electron transfer is only observed for Zn+ and Hg +. Both the radical loss and the disproportionation reaction emerge fr om a rovibrationally highly excited insertion intermediate (CH3O)(2)M( +), and for the first-row metals the branching ratio of the competing processes seems to be affected by the M(+)-OR bond strengths as well a s the electronic groundstate configurations of M(+). For the 4d and 5 d cations Ru+-Ag+ and Pt+-Au+, respectively, products resulting from i ntramolecular redox reactions dominate; this probably reflects the hig her propensity of these metal ions to facilitate beta-hydrogen atom sh ifts.