Diimines are

organic compound In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen or carbon-carbon bonds. Due to carbon's ability to catenate (form chains with other carbon atoms), millions of organic compounds are known. The ...

s containing two

imine In organic chemistry, an imine ( or ) is a functional group or organic compound containing a carbon–nitrogen double bond (). The nitrogen atom can be attached to a hydrogen or an organic group (R). The carbon atom has two additional single bo ...

(RCH=NR') groups. Common derivatives are 1,2-

diketone In organic chemistry, a dicarbonyl is a molecule containing two carbonyl () groups. Although this term could refer to any organic compound containing two carbonyl groups, it is used more specifically to describe molecules in which both carbonyls ...

s and 1,3-diimines. These compounds are used as

ligand In coordination chemistry, a ligand is an ion or molecule (functional group) that binds to a central metal atom to form a coordination complex. The bonding with the metal generally involves formal donation of one or more of the ligand's electr ...

s and as precursors to

heterocycle A heterocyclic compound or ring structure is a cyclic compound that has atoms of at least two different chemical element, elements as members of its ring(s). Heterocyclic chemistry is the branch of organic chemistry dealing with the synthesis ...

s. Diimines are prepared by

condensation reaction In organic chemistry, a condensation reaction is a type of chemical reaction in which two molecules are combined to form a single molecule, usually with the loss of a small molecule such as water. If water is lost, the reaction is also known as a ...

s where a dialdehyde or diketone is treated with amine and water is eliminated. Similar methods are used to prepare

Schiff base In organic chemistry, a Schiff base (named after Hugo Schiff) is a compound with the general structure ( = alkyl or aryl, but not hydrogen). They can be considered a sub-class of imines, being either secondary ketimines or secondary aldimine ...

s and

oxime In organic chemistry, an oxime is a organic compound belonging to the imines, with the general formula , where R is an organic side-chain and R’ may be hydrogen, forming an aldoxime, or another organic group, forming a ketoxime. O-substituted ...

1,2-Diimines

The 1,2-diketimine ligands also called α-diimines and 1,4-diazabutadienes. They are derived from the condensation of 1,2-diketones and glyoxal with amines, often

aniline Aniline is an organic compound with the formula C6 H5 NH2. Consisting of a phenyl group attached to an amino group, aniline is the simplest aromatic amine In organic chemistry, an aromatic amine is an organic compound consisting of an aroma ...

s. An example is

glyoxal-bis(mesitylimine) Glyoxal-bis(mesitylimine) is an organic compound with the formula H2C2(NC6H2Me3)2 (Me = methyl). It is a yellow solid that is soluble in organic solvents. It is classified as a diimine ligand. It is used in coordination chemistry and homogeneous c ...

, a yellow solid that is synthesized by condensation of

2,4,6-trimethylaniline 2,4,6-Trimethylaniline is an organic compound with formula (CH3)3C6H2NH2. It is an aromatic amine that is of commercial interest as a precursor to dyes. It is prepared by selective mononitration of mesitylene, avoiding oxidation of the methyl grou ...

and

glyoxal Glyoxal is an organic compound In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen or carbon-carbon bonds. Due to carbon's ability to catenate (form chains with other carbon atoms), millions of ...

. 2,2'-Bipyridine is a 1,2-diimine. 1,2-Diketimines are “

non-innocent ligand In chemistry, a (redox) non-innocent ligand is a ligand in a metal complex where the oxidation state is not clear. Typically, complexes containing non-innocent ligands are redox active at mild potentials. The concept assumes that redox reactions ...

s”, akin to the

dithiolene Dithiolene metal complexes are complexes containing 1,2-dithiolene ligands. 1,2-Dithiolene ligands, a particular case of 1,2-dichalcogenolene species, are unsaturated bidentate ligand wherein the two donor atoms are sulfur. 1,2-Dithiolene metal ...

1,3-Diimines

For example,

acetylacetone Acetylacetone is an organic compound with the chemical formula . It is a colorless liquid, classified as a 1,3-diketone. It exists in equilibrium with a tautomer . These tautomers interconvert so rapidly under most conditions that they are tre ...

(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 H NacNac, a modification of the abbreviation Hacac for the conjugate acid of

. These species form bidentate anionic ligands.

Uses

Substituted α-diimine ligands are useful in the preparation of

post-metallocene catalyst A post-metallocene catalyst is a kind of catalyst for the polymerization of olefins, i.e., the industrial production of some of the most common plastics. "Post-metallocene" refers to a class of homogeneous catalysts that are not metallocenes. This ...

s for the

polymerization In polymer chemistry, polymerization (American English), or polymerisation (British English), is a process of reacting monomer, monomer molecules together in a chemical reaction to form polymer chains or three-dimensional networks. There are ...

and copolymerization of ethylene and alkenes.{{cite journal , doi=10.1021/acscatal.5b02426, title=Palladium and Nickel Catalyzed Chain Walking Olefin Polymerization and Copolymerization, year=2016, last1=Guo, first1=Lihua, last2=Dai, first2=Shengyu, last3=Sui, first3=Xuelin, last4=Chen, first4=Changle, journal=ACS Catalysis, volume=6, pages=428–441, doi-access=free Diimines are precursors to

NHC ligand NHC could refer to: * Nag Hammadi Codex, or Nag Hammadi Codices (e.g. Nag Hammadi Codex II, NHC II, Nag Hammadi Codex XIII, NHC XIII) * New Hanover County, a county in North Carolina * New Haven County, a county in Connecticut. * The National Human ...

s by condensation with formaldehyde.

References

Imines Ligands