A new mixed group 5 metal selenide, Nb(1.41)V(0.59)Se(9)

The new mixed-metallic phase, niobium vanadium nona­selenide, (Nb(2-x)V(x))Se(9) (0.18≤ x ≤ 0.59) is isostructural with monoclinic V(2)Se(9). The structure is composed of chains of bicapped trigonal–prismatic [MSe(8)] units. The metal (M) site is occupied by statistically disordered Nb [0.706 (5)] and V [0.294 (5)] atoms. Two trigonal prisms are linked by sharing a recta­ngular face composed of two Se(2) (2−) pairs. Through three edging and capping Se atoms, the chains are extended along [101]. The chain shows alternating short [2.8847 (7) Å] and long [3.7159 (7) Å] M—M distances. The structure shows a wide range of Se—Se inter­actions. In addition to the Se(2) (2−) pairs of the recta­ngular face, an inter­mediate Se⋯Se separation [2.6584 (5) Å] is found. The amount of each metal can vary, [(Nb(2-x)V(x))Se(9), 0.18 ≤ x ≤m 0.59] and they seem to form a random substitutional solid solution. The M—M distances increase gradually by increasing the amount of Nb atoms. The classical charge-balance of the compound can be described as [M (4+)](2)[Se(2) (2−)](2)[Se(5) (4−)].