Superelectrophilic Protio Methyl- and Protio Dimethylmethyleniminium Dications.

Electronic structures and energies of superelectrophilic dications derived by protonation of methyland dimethylmethyleniminium (R'R'C=N[sup +]R'R'; R', R' = CH[sub 3] or H) ions were calculated at the ab initio MP2/6-311+G[sup **] level. The calculations identified the N-protonated isopropyleniminium dication 14 as a minimum structure. On the basis of computed energies, deprotonation energies of the global minimum structures were also calculated. The [sup 13]C NMR chemical shifts of the intriguing dication 14 were calculated using the GIAO-MP2 method. The [sup 13]C NMR chemical shifts of the isoelectronic analogue tert-butyl cation were also calculated at the same level in order to explore the effect of an additional charge in dications 14. [ABSTRACT FROM AUTHOR]