Diimines are containing two imine (RCH=NR') groups. Common derivatives are 1,2-diimines and 1,3-diimines. These compounds are used as , but they are also precursors to other organic compounds.
Preparation
Diimines are prepared by condensation reactions where a dialdehyde or diketone is treated with amine and water is eliminated.
Many are derived from the condensation of
diketone and dialdehydes with amines, often
.
The dialdehyde
glyoxal is an especially common precursor. Similar methods are used to prepare
and
.
1,2-Diimines
The 1,2-diimines are also called α-diimines and 1,4-
diazabutadienes. An example is glyoxal-bis(mesitylimine), a yellow solid that is synthesized by condensation of 2,4,6-trimethylaniline and
glyoxal.
[
2,2'-Bipyridine is a 1,2-diimine.
]
1,2-Diketimines are “non-innocent ligands”, akin to the .
1,3-Diimines
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.
Uses
Substituted α-diimine ligands are useful in the preparation of post-metallocene catalysts, which are used for the polymerization of alkenes.
1,2-Diimines are precursors to by condensation with formaldehyde.[
]
Reduction of 1,2-diimines gives diamines.[
]
