A Novel Dinuclear Ruthenium Complex Bridged through a Substituted Phenazine Ligand Formed by Ruthenium-Promoted Oxidative Assembly of 1,3-Diaminobenzene

• Published in: Chemistry : a European journal Vol. 7; no. 23; pp. 5222 - 5228
• Main Authors: Majumdar, Partha, Falvello, Larry R., Tomás, Milagros, Goswami, Sreebrata
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag GmbH 03.12.2001; WILEY‐VCH Verlag GmbH; Wiley
• Subjects: C-N coupling; Chemistry; Chemistry, Multidisciplinary; C−H activation; diimines; Physical Sciences; ruthenium; Science & Technology; structure elucidation; ORGANIC-SYNTHESIS; TRINUCLEAR RUTHENIUM; O-BENZOQUINONE DIIMINE; CRYSTAL-STRUCTURE; BUILDING-BLOCKS; REDOX PROPERTIES; AROMATIC RING AMINATION; RHODIUM COMPLEXES; TRANSITION-METALS; ruthenium; C-H activation; C-N coupling; MOLECULAR-STRUCTURES; structure elucidation; diimines
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/1521-3765(20011203)7:23<5222::AID-CHEM5222>3.0.CO;2-T

The reaction of [Ru(acac)3] (acac=acetylacetonate) with molten 1,3‐diaminobenzene affords the crystalline monometallic compound [Ru(L1)(acac)2] (1: L1=N‐(3′‐aminophenyl)1,2‐(3‐amino)benzoquinone diimine) along with an unstable dimetallic compound [Ru2(μ‐L2)(acac)4] (2: L2=N‐4,6‐bis(3′‐aminophenyl)imino‐3,5‐diimino‐hex‐1‐ene). Compound 2 transforms to a stable dimetallic compound [Ru2(μ‐L3)(acac)4] (3: L3=2‐amino‐6(3′‐aminophenyl)imino‐9‐imino‐phenazine) in boiling 2‐methoxyethanol. The above compounds are formed by ruthenium‐mediated oxidative di‐ or trimerization of the diamine with the formation of several new C−N bonds. The products have been thoroughly characterized. FAB mass spectra, along with other physicochemical data, were used for their formulations. The compounds 1, 2, and 3 display intense peaks due to their parent molecular ions at m/z 512, 916, and 914, respectively. Final characterization of complex 3 was made by single‐crystal X‐ray structure determination. The structure of 3 confirmed the formation of three new C−N bonds and the bridging ligand L3 from 1,3‐diaminobenzene. The conversion, 2→3 is an oxidative ring‐closure reaction, which is associated with dehydrogenation reactions. The monometallic compound 1, showed a reversible metal‐based anodic response at 0.35 V. On the other hand, both the compounds 2 and 3 showed a pair of well‐resolved metal‐based anodic oxidations, for which the separation between the two successive anodic responses were high (>0.4 V). In addition, all of them showed multiple cathodic responses that were in the range −1.0 to −2.0 V. Through the formation of several C−N bonds during the reaction of [Ru(acac)3] and 1,3‐diaminobenzene, the monometallic ruthenium complex 1 and two diruthenium complexes 2 and 3 were formed.