
The ''bis''-triazinyl bipyridines (BTBPs) are a class of chemical compounds which are
tetradentate ligands similar in shape to
quaterpyridine. The BTBPs are made by the reaction of
hydrazine
Hydrazine is an inorganic compound with the chemical formula . It is a simple pnictogen hydride, and is a colourless flammable liquid with an ammonia-like odour. Hydrazine is highly toxic unless handled in solution as, for example, hydrazine ...
and a 1,2-diketone (such as
hexane-3,4-dione) with 6,6'-di
cyano-2,2'-bipyridine. The dicyanobipy can be made by reacting 2,2'-
bipy with
hydrogen peroxide in
acetic acid
Acetic acid , systematically named ethanoic acid , is an acidic, colourless liquid and organic compound with the chemical formula (also written as , , or ). Vinegar is at least 4% acetic acid by volume, making acetic acid the main component ...
, (followed by the addition of
acetone) to form 2,2'-bipyridine-''N,N''-dioxide. The 2,2'-bipyridine-''N,N''-dioxide is then converted into the dicyano compound by treatment with
potassium cyanide
Potassium cyanide is a compound with the formula KCN. This colorless crystalline salt, similar in appearance to sugar, is highly soluble in water. Most KCN is used in gold mining, organic synthesis, and electroplating. Smaller applications includ ...
and
benzoyl chloride
Benzoyl chloride, also known as benzenecarbonyl chloride, is an organochlorine compound with the formula . It is a colourless, fuming liquid with an irritating odour, and consists of a benzene ring () with an acyl chloride () substituent. It i ...
in a mixture of
water and
THF.
The BTBPs were first reported as synthetic intermediates in the synthesis of quaterpyridines by a
Diels-Alder reaction of the triazine ring with tributylstannyl
acetylene
Acetylene (systematic name: ethyne) is the chemical compound with the formula and structure . It is a hydrocarbon and the simplest alkyne. This colorless gas is widely used as a fuel and a chemical building block. It is unstable in its pure ...
or
norbornadiene, after the Diels-Alder reaction a series of other reactions cause the adjunct to lose a molecule of
nitrogen and a molecule of
cyclopentadiene
Cyclopentadiene is an organic compound with the chemical formula, formula C5H6.LeRoy H. Scharpen and Victor W. Laurie (1965): "Structure of cyclopentadiene". ''The Journal of Chemical Physics'', volume 43, issue 8, pages 2765-2766. It is often ab ...
to form the pyridine ring.
The BTBPs are related to the BTPs, the BTPs are the bis-triazinyl pyridines which were introduced to solvent extraction by Z. Kolarik. By extending the central part of the BTPs the BTBPs were created.
The synthesis of the BTBPs as solvent extraction reagents was a development of the chemistry at
Reading in
Berkshire
Berkshire ( ; in the 17th century sometimes spelt phonetically as Barkeshire; abbreviated Berks.) is a historic county in South East England. One of the home counties, Berkshire was recognised by Queen Elizabeth II as the Royal County of Berk ...
which was done during the
PARTNEW EU funded project on advanced
nuclear reprocessing
Nuclear reprocessing is the chemical separation of fission products and actinides from spent nuclear fuel. Originally, reprocessing was used solely to extract plutonium for producing nuclear weapons. With commercialization of nuclear power, the ...
, the ''hemi''-BTPs had been made from 2,2'-bipyridine-''N''-oxide this chemistry was then extended to form the BTBPs. The research continued during the
EUROPART integrated project and in the ACSEPT project. With lanthanides the BTBPs bind with four nitrogens to form complexes, the tri
nitrate
Nitrate is a polyatomic ion
A polyatomic ion, also known as a molecular ion, is a covalent bonded set of two or more atoms, or of a metal complex, that can be considered to behave as a single unit and that has a net charge that is not zer ...
complexes of most of the lanthanides have been characterised by
X-ray crystallography
Crystallography is the experimental science of determining the arrangement of atoms in crystalline solids. Crystallography is a fundamental subject in the fields of materials science and solid-state physics (condensed matter physics). The wor ...
, with a smaller metal such as
nickel the BTBPs are may bind with three nitrogens in some complexes. The
perchlorate salts of both the 1:1 and 1:2 complexes of nickel and a BTBP have been characterised by crystallography. The 1:1 complex has a single BTBP which binds through four nitrogen atoms to the metal atom, the four BTBP
nitrogens form an equatorial plane and two
acetonitrile
Acetonitrile, often abbreviated MeCN (methyl cyanide), is the chemical compound with the formula and structure . This colourless liquid is the simplest organic nitrile (hydrogen cyanide is a simpler nitrile, but the cyanide anion is not clas ...
molecules occupy the two
axial
Axial may refer to:
* one of the anatomical directions describing relationships in an animal body
* In geometry:
:* a geometric term of location
:* an axis of rotation
* In chemistry, referring to an axial bond
* a type of modal frame, in music
* ...
sites. Two BTBP molecules each bind with three nitrogens in the 1:2 complex to provide the nickel with a distorted
octahedral coordination environment.
Uranium(VI) binds to BTBP to form a 1:1 complex, where the axial sites are occupied with the
uranyl oxygen atoms. The BTBPs are also able to bind to
cyclopentadienyl Cyclopentadienyl can refer to
*Cyclopentadienyl anion, or cyclopentadienide,
**Cyclopentadienyl ligand
*Cyclopentadienyl radical, •
*Cyclopentadienyl cation,
See also
*Pentadienyl
In organic chemistry, pentadienyl refers to the organic radic ...
complexes of uranium.
In recent years the BTBPs have been investigated as reagents for the
selective extraction of post-
plutonium metals such as
americium
Americium is a synthetic radioactive chemical element with the symbol Am and atomic number 95. It is a transuranic member of the actinide series, in the periodic table located under the lanthanide element europium, and thus by analogy was na ...
from
nitric acid solutions containing large amounts of
lanthanide
The lanthanide () or lanthanoid () series of chemical elements comprises the 15 metallic chemical elements with atomic numbers 57–71, from lanthanum through lutetium. These elements, along with the chemically similar elements scandium and yttr ...
s. Already one of the BTBPs has been shown to be able to selectively extract the americium and
curium
Curium is a transuranic, radioactive chemical element with the symbol Cm and atomic number 96. This actinide element was named after eminent scientists Marie and Pierre Curie, both known for their research on radioactivity. Curium was first inte ...
from a genuine mixture formed from used
MOX fuel.
The
MOX fuel was dissolved in
nitric acid, the bulk of the
uranium and
plutonium were removed by means of a
PUREX type extraction using tributyl phosphate in a hydrocarbon, the lanthanides and the remaining actinides were then separated from the aqueous residue (
raffinate) by a diamide based extraction to give, after stripping, a mixture of trivalent actinides and lanthanides.
References
{{DEFAULTSORT:Btbp
Triazines
Bipyridines
Tetradentate ligands