PUB - Publikationen an der Universität Bielefeld

Gaseous ion/neutral (1/N) complexes [R+ center dot center dot center dot C6H5CH2CH2CH2C6H5] with R = t-C4H9+, s-C4H9+ and.s-C3H7+ have been generated by protonation of the corresponding precursor compounds, R-C6H4CH2CH2CH2C6H5, in the chemical ionisation (CI) source of a sector-field mass spectrometer. The fragmentation of these I/N complexes and several deuterium-labelled isotopologues on the metastable ions' timescale (20-30 mu s), as studied by MIKE spectrometry, revealed that (i) the initial ring position (meta- or para-) of R = t-C4H9+ does not affect their infra-complex reactivity, (ii) the fragmentation of the s-C3H7+ and s-C4H9+ ions is dominated by proton transfer to the 1,3-diphenylpropane neutral but hydride ion abstraction in the reverse direction competes to a minor extent, (iii) the secondary alkyl cations exhibit the same regioselectivity (k(alpha-H)/k(omega-H) = 1.0) and kinetic isotope effect (k(H)/k(D) = 1.6) in the hydride transfer channel as do tertiary alkyl cations, (iv) the s-C4H9+ ions do not undergo skeletal isomerisation to t-C4H9+ ions within the IN complex. Attempts to characterise the trimethylsilyl complex, [Si(CH3)(3)(+) center dot center dot center dot C6H5CH2CH2CH2C6H5], by CI/MIKE: spectrometry under analogous conditions failed.