1392437-35-2Relevant academic research and scientific papers
Comparative study on ortho-C-H vs ortho-C-X (X = C, Cl, S) bond activation in ortho-Caromatic-N bond fusion in substituted anilines using ruthenium(II) mediators: Isolation and characterization of unusual Ru 2 complexes
Mandal, Sutanuva,Samanta, Subhas,Mondal, Tapan K.,Goswami, Sreebrata
, p. 5282 - 5293 (2012)
The chemical reactions of a selection of ortho-mono- and disubstituted anilines with two ruthenium polyene mediator complexes, CpRu IICl(PPh3)2 (Cp- = cyclopentadienyl anion) and (Bnz)2RuII2Cl4 (Bnz = benzene), have been undertaken with a primary aim to make a comparison between ortho-C-H and ortho-C-X (X = Cl, C, S) bond activation processes in ortho-C-N bond fusion reactions. The reaction of ortho-monosubstituted anilines, viz., 2-chloroaniline (HL1a), 2-methylaniline (HL1c), and 2-methylthioaniline (HL1b), with CpRuIICl(PPh 3)2 yielded mononuclear complexes [CpRuIIL 2a-cCl] (1, 3, and 5), containing in situ generated ligands N-(aryl)-ortho-quinonediimine, L2a-c, along with anilido-bridged RuIII2 complexes (2, [CpClRuIII{μ- η2-(L1a)-}]2; 4, [CpClRu III{μ-η2-(L1c)-}] 2; and [6]Cl2, [CpRuIII{μ-η2: η1-(L1b)-}]2), respectively. The new ligands, L2a-c are formed via ortho-C-H bond activation reactions, whereas ortho-C-X bonds remained unaffected. However, the ortho-C-Cl bond activation reaction is also noted in the reaction between CpRu IICl(PPh3)2 and ortho-disubstituted aniline 2,6-dichloroaniline (HL3a) in more forceful conditions. The ruthenium(III) binuclear complex [CpRuIII{μ-η2: η1-(L3a)-}(μ-η2: η1-L2d)(μ-η2-acetate)Ru IIICl]Cl, [7]Cl, of an in situ generated N-(2,6-dichlorophenyl)-6- chloro-ortho-quinonediimine ligand, L2d, has been isolated from the above reaction. The ligand L2d coordinates in a η2- binding mode through an imine (=NH) nitrogen atom. The coordination mode of 2,6-dichloroanilide, (L3a)-, in [7]Cl is unusual in that an aromatic-C-Cl group is coordinated to a Ru(III) center, and it represents the first authentic crystallographic evidence of such a coordination mode in a transition metal complex. Similar reactions on a redox-inert mediator complex, (Bnz)2RuII2Cl4 (Bnz = benzene), with the aforesaid aromatic amines failed to result in ortho-C-N bond fusion reactions and afforded the mononuclear anilino complexes and an anilido-bridged RuII2 compound, [9]Cl2. The complexes have been characterized by using a host of physical methods as well as single-crystal X-ray structure determination. Their redox and spectroscopic properties have been thoroughly characterized by cyclic voltammetry and UV-vis and electron paramagnetic resonance spectroscopy. Density-functional theory calculations were employed to confirm their structural features and to support the spectral and redox properties.
