Pyridazine-Based N-Heterocyclic Carbene Complexes and Ruthenium-Catalyzed Oxidation Reaction of Alkenes

• Autores: Xiaolong Liu, Wanzhi Chen
• Localización: Organometallics, ISSN 0276-7333, Vol. 31, Nº. 18, 2012, págs. 6614-6622
• Idioma: inglés
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• Resumen

  • [Ru2Cl(L)(CH3CN)4](PF6)3 (1, L = 3,6-bis(N-(pyridylmethyl)imidazolylidenyl)pyridazine), [Cu3La3](PF6)3 (2, La = 3-(N-(pyridylmethyl)imidazolylidenyl)-6-(N-(pyridylmethyl)imidazolylonyl)pyridazine), [Pd2(allyl)2L](PF6)2 (3), [Pd2(allyl)2Lb2](PF6)2 (4, Lb = N-pyridylmethylimidazole), and [NiLc2](PF6)2 (5, Lc = 3-(N-(pyridylmethyl)imidazolylidenyl)-6-methoxylpyridazine) have been synthesized and fully characterized by NMR spectroscopy, elemental analysis, and X-ray diffraction analysis. In complex 1, ligand L binds to two Ru(II) centers, forming a well-behaved Ru2(L)Cl plane with a five-membered metallocyclic ring. Complex 2 is trinuclear, containing a triangular Cu3 unit bonded together by three 3-(N-(pyridylmethyl)imidazolylidenyl)-6-(N-(pyridylmethyl)imidazolylonyl)pyridazine, where one imidazolylidene was oxidized into imidazolone. Deprotonation reaction with Ag2O in CH3CN and CH3OH resulted in C–N cleavage of the imidazolium salt, and subsequent reaction with [Pd(allyl)Cl]2 and Ni(PPh3)2Cl2 gave 4 and 5, respectively. Dinuclear Ru(II)-NHC complex 1 exhibits excellent catalytic activity for the oxidation of alkenes into diketones.