Nd 3 N 2 SeBr: Ein neues Nitridselenidbromid des Neodyms mit $\rm ^{1}_{\infty}\{[N_{2}Nd_{3}]^{3+}\}$ ‐Strängen aus hochkondensierten [NNd 4 ] 9+ ‐Tetraedern

Nd 3 N 2 SeBr: A New Nitride Selenide Bromide of Neodymium with $\rm ^{1}_{\infty}\{[N_{2}Nd_{3}]^{3+}\}$ Strands of Highly Condensed [NNd 4 ] 9+ Tetrahedra The oxidation of neodymium powder with selenium and sodium azide (NaN 3 ) in the presence of neodymium tribromide (NdBr 3 ) yields neodymium nitride selenide bromide with the composition Nd 3 N 2 SeBr when appropriate molar ratios of the reactants are used. Additional sodium bromide (NaBr) as a flux secures fast reactions (7 d) at 900 °C in evacuated silica tubes as well as the formation of dark brown single crystals. The orthorhombic crystal structure ( Pnma , Z = 4) was determined from single crystal X‐ray diffraction data ( a = 1288.13(9), b = 405.22(3), c = 1206.29(8) pm). There are three crystallographically different Nd 3+ cations present. Nd1 resides in eightfold coordination of four N 3− , two Se 2− and two Br − anions forming a square antiprism and Nd2 is coordinated by three N 3− , one Se 2− and three Br − in the shape of a monocapped trigonal prism. Finally, an octahedral coordination sphere of one N 3− , three Se 2− and two Br − anions surrounds Nd3. However, the main feature in the crystal structure comprises N 3− ‐centred (Nd 3+ ) 4 tetrahedra arranged as chains $\rm ^{1}_{\infty}\{[NNd_{2}]^{3+}\}$ of cis ‐edge connected [NNd 4 ] 9+ units first, which are further connected via two more edges to form strands $\rm ^{1}_{\infty}\{[N_{2}Nd_{3}]^{3+}\}$ of highly condensed all‐ cisoid oriented [NNd 4 ] 9+ tetrahedra. They get bundled along [010] like a hexagonal rod packing and are held together by two radiographically indistinguishable Se 2− and Br − anions, which thereby also achieve the charge balance.