NacNac is a class of anionic bidentate ligands. 1,3-Diketimines are often referred to as "HNacNac", a modification of the abbreviation Hacac used for 1,3-diketones. These species can exist as a mixture of tautomers. [1]
NacNac is a class of anionic bidentate ligands. 1,3-Diketimines are often referred to as "HNacNac", a modification of the abbreviation Hacac used for 1,3-diketones. These species can exist as a mixture of tautomers. [1]
Acetylacetone and related 1,3-diketones condense with primary alkyl- or arylamines resulting in replacement of the carbonyl oxygen atoms with NR groups, where R = aryl, alkyl. To prepare 1,3-diketimines from bulky amines, e.g. 2,4,6-trimethylanilines, prolonged reaction times are required. 2,6-Diisopropylaniline is a common bulky building block.
Deprotonation of HNacNac compounds affords anionic bidentate ligands that form a variety of coordination complexes. [2] Some derivatives with large R groups can be used to stabilize low valent main group and transition metal complexes. [3] Unlike the situation for the acetylacetonates, the steric properties of the coordinating atoms in NacNac− ligands is adjustable by changes in the R substituent. Attachment to a metal center is usually carried out by initial deprotonation of HNacNac with n-butyllithium; the lithium derivative is then treated with a metal chloride to eliminate lithium chloride. In some cases, HNacNacs also serve as charge-neutral 1,3-diimine ligands.
![Structure of [(C6H3-2,6-(i-Pr)2)2NacNac]NiSCPh3 viewed down the C2 axis, illustrating the steric bulk of this NacNac ligand (CPh3 removed for clarity). Color code=gray = C, white = H, blue=N, yellow=S, green=Ni). FUYTEAfragment.png](http://upload.wikimedia.org/wikipedia/commons/thumb/0/02/FUYTEAfragment.png/220px-FUYTEAfragment.png)
NacNac ligands are diimine analogues of acetylacetonate ligands. An intermediate class of ligands are derived from monoimino-ketones. [5] [6] The first Dipp-NacNac ligand was synthesized by Dr. Francis S. Mair in 1998. [7]
In organic chemistry, a diene ; also diolefin, dy-OH-lə-fin) or alkadiene) is a covalent compound that contains two double bonds, usually among carbon atoms. They thus contain two alkene units, with the standard prefix di of systematic nomenclature. As a subunit of more complex molecules, dienes occur in naturally occurring and synthetic chemicals and are used in organic synthesis. Conjugated dienes are widely used as monomers in the polymer industry. Polyunsaturated fats are of interest to nutrition.
In organometallic chemistry, organolithium reagents are chemical compounds that contain carbon–lithium (C–Li) bonds. These reagents are important in organic synthesis, and are frequently used to transfer the organic group or the lithium atom to the substrates in synthetic steps, through nucleophilic addition or simple deprotonation. Organolithium reagents are used in industry as an initiator for anionic polymerization, which leads to the production of various elastomers. They have also been applied in asymmetric synthesis in the pharmaceutical industry. Due to the large difference in electronegativity between the carbon atom and the lithium atom, the C−Li bond is highly ionic. Owing to the polar nature of the C−Li bond, organolithium reagents are good nucleophiles and strong bases. For laboratory organic synthesis, many organolithium reagents are commercially available in solution form. These reagents are highly reactive, and are sometimes pyrophoric.
Polysulfides are a class of chemical compounds derived from anionic chains of sulfur atoms. There are two main classes of polysulfides: inorganic and organic. The inorganic polysulfides have the general formula S2−
n. These anions are the conjugate bases of polysulfanes H2Sn. Organic polysulfides generally have the formulae R1SnR2, where R = alkyl or aryl.
Acetylacetone is an organic compound with the chemical formula CH3−C(=O)−CH2−C(=O)−CH3. It is classified as a 1,3-diketone. It exists in equilibrium with a tautomer CH3−C(=O)−CH=C(−OH)−CH3. The mixture is a colorless liquid. These tautomers interconvert so rapidly under most conditions that they are treated as a single compound in most applications. Acetylacetone is a building block for the synthesis of many coordination complexes as well as heterocyclic compounds.
The Ullmann reaction or Ullmann coupling, named after Fritz Ullmann, couples two aryl or alkyl groups with the help of copper. The reaction was first reported by Ullmann and his student Bielecki in 1901. It has been later shown that palladium and nickel can also be effectively used.
A persistent carbene (also known as stable carbene) is a type of carbene demonstrating particular stability. The best-known examples and by far largest subgroup are the N-heterocyclic carbenes (NHC) (sometimes called Arduengo carbenes), for example diaminocarbenes with the general formula (R2N)2C:, where the four R moieties are typically alkyl and aryl groups. The groups can be linked to give heterocyclic carbenes, such as those derived from imidazole, imidazoline, thiazole or triazole.
Tm is an abbreviation for anionic tridentate ligand based on three imidazole-2-thioketone groups bonded to a borohydride center. They are examples of scorpionate ligands. Various ligands in this family are known, differing in what substituents are on the imidazoles. The most common is TmMe, which has a methyl group on the nitrogen. It is easily prepared by the reaction of molten methimazole (1-methylimidazole-2-thione) with sodium borohydride, giving the sodium salt of the ligand. Salts of the TmMe anion are known also for lithium and potassium. Other alkyl- and aryl-group variations are likewise named TmR according to those groups.
Organocopper chemistry is the study of the physical properties, reactions, and synthesis of organocopper compounds, which are organometallic compounds containing a carbon to copper chemical bond. They are reagents in organic chemistry.
In organic chemistry, the Buchwald–Hartwig amination is a chemical reaction for the synthesis of carbon–nitrogen bonds via the palladium-catalyzed coupling reactions of amines with aryl halides. Although Pd-catalyzed C–N couplings were reported as early as 1983, Stephen L. Buchwald and John F. Hartwig have been credited, whose publications between 1994 and the late 2000s established the scope of the transformation. The reaction's synthetic utility stems primarily from the shortcomings of typical methods for the synthesis of aromatic C−N bonds, with most methods suffering from limited substrate scope and functional group tolerance. The development of the Buchwald–Hartwig reaction allowed for the facile synthesis of aryl amines, replacing to an extent harsher methods while significantly expanding the repertoire of possible C−N bond formations.
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 in metal complexes are either metal or ligand localized, which is a simplification, albeit a useful one.
Organoiron chemistry is the chemistry of iron compounds containing a carbon-to-iron chemical bond. Organoiron compounds are relevant in organic synthesis as reagents such as iron pentacarbonyl, diiron nonacarbonyl and disodium tetracarbonylferrate. While iron adopts oxidation states from Fe(−II) through to Fe(VII), Fe(IV) is the highest established oxidation state for organoiron species. Although iron is generally less active in many catalytic applications, it is less expensive and "greener" than other metals. Organoiron compounds feature a wide range of ligands that support the Fe-C bond; as with other organometals, these supporting ligands prominently include phosphines, carbon monoxide, and cyclopentadienyl, but hard ligands such as amines are employed as well.
Nickel(II) bis(acetylacetonate) is a coordination complex with the formula [Ni(acac)2]3, where acac is the anion C5H7O2− derived from deprotonation of acetylacetone. It is a dark green paramagnetic solid that is soluble in organic solvents such as toluene. It reacts with water to give the blue-green diaquo complex Ni(acac)2(H2O)2.
Metal acetylacetonates are coordination complexes derived from the acetylacetonate anion (CH
3COCHCOCH−
3) and metal ions, usually transition metals. The bidentate ligand acetylacetonate is often abbreviated acac. Typically both oxygen atoms bind to the metal to form a six-membered chelate ring. The simplest complexes have the formula M(acac)3 and M(acac)2. Mixed-ligand complexes, e.g. VO(acac)2, are also numerous. Variations of acetylacetonate have also been developed with myriad substituents in place of methyl (RCOCHCOR′−). Many such complexes are soluble in organic solvents, in contrast to the related metal halides. Because of these properties, acac complexes are sometimes used as catalyst precursors and reagents. Applications include their use as NMR "shift reagents" and as catalysts for organic synthesis, and precursors to industrial hydroformylation catalysts. C
5H
7O−
2 in some cases also binds to metals through the central carbon atom; this bonding mode is more common for the third-row transition metals such as platinum(II) and iridium(III).
Diiminopyridines are a class of diimine ligands. They featuring a pyridine nucleus with imine sidearms appended to the 2,6–positions. The three nitrogen centres bind metals in a tridentate fashion, forming pincer complexes. Diiminopyridines are notable as non-innocent ligand that can assume more than one oxidation state. Complexes of DIPs participate in a range of chemical reactions, including ethylene polymerization, hydrosilylation, and hydrogenation.
Tris(oxazolinyl)borate compounds are a class of tridentate ligands; often abbreviated ToR, where R is the substituent on the oxazoline ring. Most commonly the substituent is either a methyl, propyl, tert-butyl or hydrogen. The formation of anionic boron backbone with addition of a phenyl group on boron allows the ligand to strongly bind to the metal center. It results in a more robust complex.
Diimines are organic compounds containing two imine (RCH=NR') groups. Common derivatives are 1,2-diketones and 1,3-diimines. These compounds are used as ligands and as precursors to heterocycles. Diimines are prepared by condensation reactions where a dialdehyde or diketone is treated with amine and water is eliminated. Similar methods are used to prepare Schiff bases and oximes.
In coordination chemistry, a transition metal NHC complex is a metal complex containing one or more N-heterocyclic carbene ligands. Such compounds are the subject of much research, in part because of prospective applications in homogeneous catalysis. One such success is the second generation Grubbs catalyst.
2,6-Diisopropylaniline is an organic compound with the formula H2NC6H3(CHMe2)2 (Me = CH3). It is a colorless liquid although, like many anilines, samples can appear yellow or brown. 2,6-Diisopropylaniline is a bulky aromatic amine that is often used to make ligands in coordination chemistry. The Schrock carbenes often are transition metal imido complexes derived from this aniline. Condensation with diacetylpyridine and acetylacetone gives, respectively, diiminopyridine and NacNac ligands.
Francis S. Mair is a British chemist and a Senior Lecturer in the Department of Chemistry at The University of Manchester. His research is based on synthetic chemistry, inorganic chemistry, catalysis and polymer chemistry.
Gallylenes are a class of gallium species which are electronically neutral and in the +1-oxidation state. This broad definition may include many gallium species, such as oligomeric gallium compounds in which the gallium atoms are coordinated to each other, but these classes of compounds are often referred to as gallanes. In recent literature, the term gallylene has mostly been reserved for low valent gallium species which may have a lone pair, analogous to NHC's or terminal borylenes. They are compounds of academic interest because of their distinctive electronic properties which have been achieved for higher main group elements such as borylenes and carbenes.