Dissociation of CuH+ and ZnH+ complexes of ethylenediamine and their N-methylated homologues: Family and neighbours, but not the same
International Journal of Mass Spectrometry , Volume 354-355 p. 144- 151
Upon collisional activation, complexes of CuH+ and ZnH + with H2NCH2CH2NH2 eliminate Cu(0) and Zn(0) to produce protonated ethylenediamine H 2NCH2CH2NH3 + via a proton transfer. Variable collision energy experiments and model chemistry calculations (CBS-QB3 method) indicate that (i) the energy requirement for this process is significantly larger for the zinc complex than for the copper complex; and (ii) the transition-state for the proton transfer is rate-determining for dissociation of the zinc complex, whereas the same process in the copper complex is essentially barrierless. The large activation energy for the zinc complex opens up a competing fragmentation process, viz. loss of NH3, which does not occur in the copper complex. N-methyl substitution has no effect for the CuH+ complex ions: Cu(0) is lost from the complex (CH3)2NCH2CH 2N(CH3)2 CuH+. However, a different situation obtains for the complex with ZnH+, which predominantly loses ZnH2. Experiment and theory indicate that loss of ZnH 2 is more energy demanding than loss of Zn(0), but that ZnH 2 loss prevails at elevated collision energies.
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Jobst, K.J, Terlouw, J.K, Ruttink, P.J.A, & Burgers, P.C. (2013). Dissociation of CuH+ and ZnH+ complexes of ethylenediamine and their N-methylated homologues: Family and neighbours, but not the same. International Journal of Mass Spectrometry, 354-355, 144–151. doi:10.1016/j.ijms.2013.06.010