This article is about the class of compounds having two imine groups. For compound having the molecular formula N2H2 and often called "diimine", see diazene.
Diimines are organic compounds containing two imine (RCH=NR') groups. Common derivatives are 1,2-diimines and 1,3-diimines. These compounds are used as ligands, but they are also precursors to other organic compounds.[1]
Diimines are prepared by condensation reactions where a dialdehyde or diketone is treated with amine and water is eliminated.[2] Many are derived from the condensation of 1,2-diketones and dialdehydes with amines, often anilines.[3] The dialdehyde glyoxal is an especially common precursor. Similar methods are used to prepare Schiff bases and oximes.
1,2-Diimines
Sample of alpha-diimine derived from 2,6-diisopropylaniline and glyoxal.A substituted 1,2-diimine ligand and an idealized metal complex.
For example, acetylacetone (2,4-pentanedione) and a primary alkyl- or arylamine will react, typically in acidified ethanol, to form a diketimine. 1,3-Diketimines are often referred to as HNacNac, a modification of the abbreviation Hacac for the conjugate acid of acetylacetone. These species form bidentate anionic ligands.
N,N'-di(propan-2-yl)ethane-1,2-diimine is a riot control agent that is synthesized by the condensation of glyoxal with isopropyl amine. Inhalation of 5mg can lead to irritation and congestion.[10]
1 2 Ison, Elon A.; Ison, Ana (2012). "Synthesis of Well-Defined Copper N-Heterocyclic Carbene Complexes and Their Use as Catalysts for a "Click Reaction": A Multistep Experiment That Emphasizes the Role of Catalysis in Green Chemistry". J. Chem. Educ. 89 (12): 1575–1577. Bibcode:2012JChEd..89.1575I. doi:10.1021/ed300243s.
↑ Mashima, Kazushi (2020). "Redox-Active α-Diimine Complexes of Early Transition Metals: From Bonding to Catalysis". Bulletin of the Chemical Society of Japan. 93 (6): 799–820. doi:10.1246/bcsj.20200056.
↑ Asay, Matthew; Jones, Cameron; Driess, Matthias (2011-02-09). "N-Heterocyclic Carbene Analogues with Low-Valent Group 13 and Group 14 Elements: Syntheses, Structures, and Reactivities of a New Generation of Multitalented Ligands†". Chemical Reviews. 111 (2): 354–396. doi:10.1021/cr100216y. ISSN0009-2665. PMID21133370.
↑ Ellison, D. Hank (2007-08-24). Handbook of Chemical and Biological Warfare Agents, Second Edition. Boca Raton, Fla.: CRC Press. p.63. ISBN978-0-8493-1434-6.
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