The First Imido Complex of Osmium(VI), [CpOs(NH)(CH₂SiMe₃)₂][SO₃CF₃]

Protonation of Os(η5-C5H5)(N)(CH2SiMe3)2 with either HBF4 or CF3SO3H at low temperature produces a thermally unstable imido complex, [Os(η5-C5H5)(NH)(CH2SiMe3)2][X] (X = BF4, SO3CF3). The imido complex is a strong acid and readily deprotonates. A similar reaction between the nitridoosmium complex and [AuPPh3][BF4] forms a gold adduct, [Os(η5-C5H5)(NAuPPh3)(CH2SiMe3)2][BF4]. Each of the two complexes has a three-legged piano stool molecular structure, but the Os−N distance in the imido ligand is longer than that in the gold adduct. Lewis bases displace (triphenylphosphine)gold from the osmium nitrido group.