Addition of carbenes to an osmium(VI) nitride complex

A series of osmium(vi) nitride complexes containing 8-quinolinolato ligands, [Os-VI(N)(X-Q)(2)Cl] (X = H, 5-Cl, 5-NO2, 2-Me; 1a-d), have been synthesized by reaction of HX-Q with [nBu(4)N][O-s(VI)(N)Cl-4] in the presence of 2,6-dimethylpyridine. The v(Osequivalent toN) 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 Osequivalent toN bond distance is 1.644(6) Angstrom. Complex 1c readily reacts with the carbene precursors bis(1,3-dialkylimidazolidin-2-ylidene) (L-2(R); R = Me, Et, or CH2Ph) to produce the osmium(IV) azavinylidene species, [Os-IV(N=L-R)(NO2-Q)(2)Cl], which are derived from the formal addition of the carbenes L-R to Os(VI)equivalent toN. The structure of [Os-IV(N=L-Et)(NO2-Q)(2)Cl] (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) Angstrom is rather long and, together with the rather acute Os(1)-N(5)-C(19) angle of 133.8(5)degrees, indicates that there is no significant multiple-bond character in the Os(1)-N(5) bond. (C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005.