It hydrolyzes in air, and samples are often contaminated with small amounts of NbOCl3.

[1] Niobium(V) chloride forms chloro-bridged dimers in the solid state (see figure).

Each niobium centre is six-coordinate, but the octahedral coordination is significantly distorted.

The conversion can be effected with thionyl chloride:[4] It also can be prepared by chlorination of niobium pentoxide in the presence of carbon at 300 °C.

Niobium chloride can also generate N-acyliminium compounds from certain pyrrolidines which are substrates for nucleophiles such as allyltrimethylsilane, indole, or the silyl enol ether of benzophenone.