Noble gas catalysed 1,2-migrations in N2H+ and N2CH3+

Molecular orbital calculations are reported for N2H+ and N2CH3+ and for the transition structures for the rearrangement of these ions by 1,2-shifts of Ei and CH3. All reaction profiles were also calculated with one atom of no ble gas, M, present (M = Ne, Ar, Kr). Structure optimizations were performe d at B3LYP/6-311++G(d,p) and, in the case of N2H+... M, single point calcul ations were also performed at QCISD(T)(full)/G-311++G(2df.p). For N2H+, inc lusion of one noble gas atom reduces the barrier to rearrangement from 46.6 kcal mol(-1) for the uncatalysed reaction to 47.6 kcal mol(-1) (by Ne), to 21.4 kcal mol(-1) (by Ar), and to 11.0 kcal mol(-1) (by Kr). For N2CH3+, t he barrier of 36.4 kcal mol(-1) is reduced to 35.1 kcal mol(-1) by Ne, to 2 7.4 kcal mol(-1) by Ar, and to 18.4 kcal mol(-1) by Kr.