Abstract
A series of cyclic hydrocarbons were introduced to react with V^+^ and Ta^+^ using a pulsed beam expansion source in a time‐of‐flight mass spectrometer. The third‐row metal Ta^+^ displayed high reactivity in dehydrogenation to form benzyne complexes, whereas benzene complexes were the terminal products for V^+^. M^+^–C~6~H~6~ (M^+^ = V^+^ and Ta^+^) and Ta^+^–C~6~H~4~ were selected to perform the photodissociation experiments. In contrast to the V^+^ fragment formation via simple cleavage of the V^+^–C~6~H~6~ bond, a photoinduced loss of C~2~H~2~ occurred in both the Ta^+^–C~6~H~6~ and Ta^+^–C~6~H~4~ complexes. Plausible explanations involved in the formation of Ta^+^–C~6~H~6~ and Ta^+^–C~6~H~4~ complexes are given for observing such photo‐induced dissociation. The observed photodissociation in Ta^+^–C~6~H~6~ is analogous to the dissociative process previously investigated in metal ion–molecule reactions. The photodissociation spectrum of Ta^+^–C~6~H~4~ was obtained by recording the appearance of Ta^+^–C~4~H~2~ as a function of wavelength and yielded a dissociation energy of 91 ± 1 kcal mol^−1^. Copyright © 2001 John Wiley & Sons, Ltd.