Monocapped Trigonal‐Prismatic Transition‐Metal Heptaazides: Syntheses, Properties, and Structures of [Nb(N₃)₇]²⁻ and [Ta(N₃)₇]²⁻

Structures with a bang: The title anions are the first examples of doubly charged heptaazido anions and structurally characterized transition-metal heptaazides. Contrary to the either monocapped octahedral or pentagonal-bipyramidal actinide trianion [U(N3)7]3−, but in accord with the [NbF7]2− anion, the title anions have monocapped trigonal-prismatic structures (see picture; M=Nb, Ta).