Addition of carbenes to an osmium(VI) nitride complex

A series of osmium(VI) nitride complexes containing 8-quinolinolato ligands, [Osⱽᴵ(N)(X-Q)₂Cl] (X = H, 5-Cl, 5-NO₂, 2-Me; 1a-d), have been synthesized by reaction of HX-Q with [nBu₄N][Osⱽᴵ(N)Cl₄] in the presence of 2,6-dimethylpyridine. The v(Os≡N) stretches of these compounds occur at 1056-1075 cm⁻¹, and are within the range (1050-1120 cm⁻¹) found for most osmium nitride species. The structure of 1d has been determined by X-ray crystallography. The osmium center adopts a distorted octahedral geometry, and the two quinolinolato ligands are cis to each other. The three N atoms are in a facial arrangement, and the Os≡N bond distance is 1.644(6) Å. Complex 1c readily reacts with the carbene precursors bis(1,3-dialkylimidazolidin-2-ylidene) (Lᴿ₂; R = Me, Et, or CH₂Ph) to produce the osmium(IV) azavinylidene species, [Osᴵⱽ(N=Lᴿ)(NO₂-Q)₂Cl], which are derived from the formal addition of the carbenes Lᴿ to Osⱽᴵ≡N. The structure of [Osᴵⱽ(N=Lᴱᵗ) (NO₂₋Q)₂Cl] (2b) has been determined by X-ray crystallography. The osmium center has a distorted octahedral geometry in which the facial arrangement of the three N atoms is retained. The Os(1)-N(5) distance of 1.875(6) Å is rather long and, together with the rather acute Os(1)-N(5)-C(19) angle of 133.8(5)°, indicates that there is no significant multiple-bond character in the Os(1)-N(5) bond. Copyright © 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.