Imidazolidine ligands and their coordination behaviour towards the fac-[Re(CO)3]+ core: Unusual synthetic route, spectroscopic and X-Ray crystallographic characterization

This study highlights the unusual synthetic route that led to a series of the unexpected ring-containing benzimidazolidines and imidazolidines, obtained from the reaction of ketone and diamino-containing compounds. The reaction of the bridging pyridyl; 2,2′-dipyridylketone (dpk) with 1,2-diaminobenzene and 1,2-diaminoethane in methanol led to the isolation of 2,3-dihydro-2,2-di(pyridin-2-yl)-1H-benzo[d]imidazole (H2dpb) and 2-(2-(pyridine-2-yl)imidazolidin-2-yl)pyridine (H2pip) respectively. The compounds fac-[Re(CO)3(H2dmb)Cl] (1) and fac-[Re(CO)3(H2pip)]Cl.H2O (2) were isolated in good yield by reacting [Re(CO)5Cl] with 2,3-dihydro-2,2-di(pyridin-2-yl)-1H-benzo[d]imidazole (H2dpb) and 2-(2-(pyridine-2-yl)imidazolidin-2-yl)pyridine (H2pip) in toluene respectively. A surprising aspect of fac-[Re(CO)3(H2dmb)Cl] (1) is the benzimidazolidine ring opening in H2dpb, which resulted in the formation of the neutrally coordinated Schiff-base ligand, N1-(di(pyridine-2-yl)methylene)benzene-1,2-diamine (H2dmb), which acts as a bidentate N,N-donor chelate. On other hand, the H2pip ligand did not undergo any modification. Therefore, it acted as a tridentate N3,O-donor ligand towards the cationic cluster compound with a fac-[Re(CO)3]+ core. The crystal structure of H2dpb, 1 and 2 were determined by X-ray single crystal diffraction, in addition to IR, 1H NMR and electronic analysis.Graphical abstract

Source: Journal of Organometallic Chemistry - November 20, 2019 Category: Chemistry Source Type: research