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.
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.
^ abIson, 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.
^Haaf, Michael; Schmedake, Thomas A.; West, Robert (2000-10-01). "Stable Silylenes". Accounts of Chemical Research. 33 (10): 704–714. doi:10.1021/ar950192g. ISSN0001-4842. PMID11041835.
^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.