Crystal and molecular structure of a µ-hyponitrito-bis[penta-amminecobalt(III)] salt: the nature of the red nitrosylpenta-amminecobalt(III) cation

Abstract

The structure of the title cation, µ-hyponitrito-bis[penta-amminecobalt(III)], has been determined as a mixed bromide–nitrate salt from single-crystal three-dimensional X-ray photographic data, the stoicheiometry of the crystals used being [Co(NH₃)₅NO]₂Br_{3 –x}(NO₃)_{1 +x},2H₂O, where x=ca. 0·5. The structure was solved by Patterson and Fourier methods, and refined by least-squares techniques to R 0·13 for 1264 independent reflections. The complex cation is binuclear with the two metal atoms bridged by a hyponitrito-group in a cis-asymmetric manner via a nitrogen atom and the oxygen atom bonded to the other nitrogen atom of the hyponitrite group. The unit cell is monoclinic with Z= 4, a= 13·72(3), b= 7·00(2), c= 23·65(4)Å, β= 100·4(2)°, space group A2/m.