[OsCl5(H2O)]−: A novel complex in osmium chemistry; reaction chemistry and solid-state structure of [AsPh4][OsCl5(H2O)]

[OsCl5(H2O)]− (2) can be isolated by solvent extraction with P(O)(OnBu)3 from a product mixture obtained by the reduction of OsO4 in a chloride-containing medium. The X-ray structure analysis of [AsPh4][OsCl5(H2O)] (8) is reported. The reaction chemistry of 8 towards different Lewis-bases, such as EtOH, py, pyz is studied.