The crystal structure of NbO2I - A double-layer structure with 7-coordinated niobium

Single crystals of NbO2I were obtained as dark red needles by chemical transport. According to the structure determination (Pnma, a = 20.897(4), b = 3.7654(8), c = 3.9715(8) Å, Z = 4, 619 reflections, 26 variables, R1(F) = 0.0645, wR2(F2) = 0.1597) NbO2I represents a new structure type with 7-coordinated Nb atoms. Pentagonal bipyramids NbO5I2 are connected via the apical O atoms with alternating short and long Nb-O distances (1.79 / 2.20 Å) to chains and via the three equatorial O atoms to double layers. Between the double layers there are only weak van-der-Waals interactions of the I atoms. NbO 2I is the first oxide halide of a transition metal with CN 7. Structurally NbO2I is closely related to UO2Br, but with alternating short and long Nb-O distances as a difference. © 2007 Verlag der Zeitschrift für Naturforschung.