The Cluster Polyazide Complexes: Synthesis, Crystal Structures, and 14 N NMR Studies of [{Re 3 (μ-X) 3 }(N 3 ) 9 ] 3- (X = Br or I).

Azide cluster complexes [{Re 3 (μ-Br) 3 }(N 3 ) 9 ] 3- and [{Re 3 ( μ -I) 3 }(N 3 ) 9 ] 3- were obtained by reaction of Re 3 X 9 (X = Br or I, respectively) with sodium azide in methanol. The complexes were crystallized as cesium salts of the compositions Cs 3 [{Re 3 (μ-Br) 3 }(N 3 ) 9 ]·H 2 O ( 1 ) and Cs 3 [{Re 3 (μ-I) 3 }(N 3 ) 9 ]·H 2 O ( 2 ) and characterized by X-ray single-crystal diffraction and elemental analyses, mass spectrometry, 14 N NMR spectroscopy, and DFT calculations. In the anions, each rhenium atom is coordinated by three azide ligands. To the best of our knowledge, these compounds represent the first case of metal cluster polyazide complexes (i.e., where each metal atom bears more than one azide ligand). Both complexes are stable in air but are very shock sensitive, and spontaneous explosive decomposition is also possible.