Pentamethylcyclopentadienyl rhodium and iridium complexes containing oxinato ligands

The neutral chloro complexes [(g-C5Me5)M(g-NC9H6O)Cl] as well as the cationic aqua complexes [(g-C5Me5)M(g-NC9H6O)(H2O)] (M = Rh, Ir) have been synthesized from the reaction of the dinuclear precursors [(g-C5Me5)MCl2]2 and 8-hydroxyquinoline. The single crystal X-ray structure analysis of [(g-C5Me5)Ir(g-NC9H6O)Cl] reveals for these complexes a piano-stool arrangement with the aromatic ligand, the chelating oxinato ligand and the terminal chloro or aqua ligand surrounding the metal center in a pseudo-tetrahedral fashion. 8-Hydroxyquinoline, NC9H6OH (‘‘oxine”), reacts with many metal cations under deprotonation to give complexes in which the oxinato moiety NC9H6O acts as g-chelating ligand [1]. Oxinato complexes such as Mg(g-NC9H6O)2, Zn(g-NC9H6O)2 and Al(gNC9H6O)3 are used since 1930s in classical analytical chemistry [2]. The oxinato ligand is also well known in organometallic complexes; however, while arene ruthenium and osmium complexes containing an oxinato ligand have been reported [(g-MeC6H4Pr)Ru(g-NC9H6O)Cl] [3] and [(g-MeC6H4Pr)Os(g-NC9H6O)Cl] [4], to the best of our knowledge, the isoelectronic pentamethylcyclopentadienyl rhodium and iridium complexes are not known so far. We now report the synthesis and characterization of the neutral chloro complexes [(g-C5Me5)M(g-NC9H6O)Cl] and of the cationic aqua complexes [(g-C5Me5)M(g-NC9H6O)(H2O)] derived thereof. The dinuclear pentamethylcyclopentadienyl complexes [(g-C5 Me5)MCl2]2 (M = Rh, Ir) react in chloroformwith potassium oxinate at room temperature to give the neutral chloro complexes [(g-C5Me5)Rh(g-NC9H6O)Cl] (1) and [(g-C5Me5)Ir(g-NC9H6O) Cl] (2). Both complexes 1 and 2, isolated by precipitation with diethyl ether and purified by thin-layer chromatography, form air-stable, yellow to orange crystalline solids which are well soluble in dichloromethane or in chloroform [5]. [(η-C5Me5)MCl2]2 [(η-C5Me5)M(NC9H6O)Cl] 2 NC9H6OK 2 KCl + +