The triazidocarbenium cation, C(N3)3 +, was successfully combined with the energetic N(NO2)2 - and ClO4 - anions in the form of highly energetic salts. The new C(N3)3 +BF4 - salt was also prepared, and all compounds were characterized by their material balances and vibrational spectroscopy. Electronic structure calculations were carried out for C(N3)3 + at the B3LYP/6-31G*, B3LYP/cc-pVDZ, B3LYP/cc-pVTZ, and HF/cc-pVDZ levels of theory. At all levels, the energy minimum is the planar C 3 h structure, and the vibrational spectra were assigned and analyzed for this structure. The heats of formation of C(N3)3 +N(NO2)2 - and C(N3)3 +ClO4 - were estimated to be endothermic by 252 and 218 kcal mol-1 and explain the high explosive power of these salts.

The crystal structure of the cumyl cation (1; 2-phenyl-2-propyl cation) has been determined at -124°C (as hexafluoroantimonate, 1‚SbF 6 ; R 1 ) 0.0502, wR 2 ) 0.1054). The cation 1 is nearly planar and has a short C + -C ipso bond (1.41(2) Å) and bond lengths in the phenyl ring which agree with strong benzylic delocalization. The weak but distinct shortening of the C + -CH 3 bonds by 0.025(12) Å indicates weak C-H hyperconjugation. Nearly all H atoms are involved in H‚‚‚F contacts to SbF 6 anions, and one close C + ‚‚‚F contact (3.11(2) Å) is observed. The phenyl rings form infinite stacks and are shifted against each other in the stack.