Preparation and reactivity of p-cymene complexes of ruthenium and osmium incorporating 1,3-triazenide ligands

p-Cymene complexes MCl2(η6-p-cymene)L [M = Ru, Os; L = P(OEt)3, PPh(OEt)2, (CH3)3CNC] were prepared by allowing [MCl(μ-Cl)(η6-p-cymene)]2 to react with phosphites or tert-butyl isocyanide. Treatment of MCl2(η6-p-cymene)L complexes with 1,3-ArNNN(H)Ar triazene and an excess of NEt3 gave the cationic triazenide derivatives [M(η2-1,3-ArNNNAr)(η6-p-cymene)L]BPh4 (Ar = Ph, p-tolyl). Neutral triazenide complexes MCl(η2-1,3-ArNNNAr)(η6-p-cymene) (M = Ru, Os) were also prepared by allowing [MCl(μ-Cl)(η6-p-cymene)]2 to react with 1,3-diaryltriazene in the presence of triethylamine. p-Cymene complexes MCl2(η6-p-cymene)L reacted with equimolar amounts of 1,3-ArNNN(H)Ar triazene to give both triazenide complexes [M(η2-1,3-ArNNNAr)(η6-p-cymene)L]BPh4 and amine derivatives [MCl(ArNH2)(η6-p-cymene)L]BPh4. A reaction path for the formation of the amine complex is also reported. The complexes were characterised by spectroscopy and X-ray crystallography of RuCl2(η6-p-cymene)[PPh(OEt)2] and [Ru(η2-1,3-p-tolyl-NNN-p-tolyl)(η6-p-cymene){CNC(CH3)3}]BPh4. Selected triazenide complexes were studied as catalysts in the hydrogenation of 2-cyclohexen-1-one and cinnamaldehyde.

Graphical abstractThe preparation of triazenide complexes of ruthenium and osmium stabilised by the half-sandwich fragment [M(η6-p-cymene)L]+ with phosphite or isocyanide is described. Reaction of diaryltriazene, 1,3-ArNNN(H)Ar, toward complexes MCl2(η6-p-cymene)L leading to amine derivatives [MCl(ArNH2)(η6-p-cymene)L]BPh4 is also reported. The spectroscopic and crystallographic characterisation of new compounds, as well as their activity as catalysts in hydrogenation reactions, are also discussed.Figure optionsDownload full-size imageDownload as PowerPoint slide