A long Nb=O double bond in bis(pyridinium) tetra­chlorooxo(pyridine‐κN)niobate(V) chloride

The asymmetric unit of the title compound, (C₅H₆N)₂NbCl₄O(C₅H₅N)]Cl or (pyH)₂O=NbCl₄(py)]Cl (py is pyridine), contains a discrete anionic niobium(V) complex, O=NbCl₄(py)]^?, and two protonated pyridine mol­ecules, which form medium–strong hydrogen bonds with the Cl^? counter‐ion. The Nb=O distance of 1.7643 (17) Å is the longest among those in congener niobium complexes reported to date. Extensive density functional theory studies of conformations of O=NbCl₄(py)]^? and structural data mining raise doubts regarding the reliability of the length of this Nb=O double bond.