Bis(6-hydroxy-6,8,8′-trimethyl-5-aza-1-azonia-bicyclo[3.3.0]octa-1,3-diene) osmium hexachloride: synthesis and solid-state structure

Abstract

The title compound is accessible by the reaction of OsO 4 ( 1) with pyrazole (pz) in the presence of HCl in acetone as solvent. As intermediate the osmium(VI) transition metal complex trans-[OsO 2Cl 2(pz) 2] ( 3) is formed. A possible mechanism for the formation of [C 6H 5N 2Me 3(OH)] 2OsCl 6 ( 4) is presented. Compound 4 crystallises in the triclinic space group P 1 ̄ with cell parameters a=7.8993(1), b=9.3019(1), c=10.1790(1) Å, α=114.397(1), β=100.527(1), γ=96.014(1)°, Z=1 and V=4848.67(10) Å 3. The 5-aza-1-azonia-bicyclo[3.3.0]octa-1,3-diene cation consists of a planar and a saturated envelope-structured C 3N 2 five-membered cycle of which the two nitrogen atoms are the connecting points for the bicyclic unit. As counter-ion [OsCl 6] 2− is acting. The osmium chloride distances are 2.3301(8), 2.3538(8) and 2.3365(8) Å. Typical separations for the bicyclic [C 6H 3N 2Me 3(OH)] + building blocks are: NN 1.344(4), NC [aliphatic ring 1.488(4), 1.499(4) Å; aromatic ring: 1.337(4), 1.339(4) Å] and CC [aliphatic ring: 1.527(5), 1.534(5) Å; aromatic ring: 1.384(5), 1.390(5) Å].