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 [nBu 4N][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, [Os IV(N=LR)(NO2-Q)2Cl], which are derived from the formal addition of the carbenes LR to Os VI≡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. KGaA, 2005.