BTBP
Encyclopedia
The bis-triazinyl bipyridines (BTBPs) are a class of chemical compounds which are tetradentate ligand
s similar in shape to quaterpyridine. The BTBPs are made by the reaction of hydrazine
and a 1,2-diketone (such as hexane-3,4-dione) with 6,6'-dicyano-2,2'-bipyridine. The dicyanobipy can be made by reacting 2,2'-bipy with hydrogen peroxide
in acetic acid
, (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
and benzoyl chloride
in a mixture of water
and THF
.
The BTBPs were first reported as synthetic intermidates in the synthesis of quaterpyridines by a Diels-Alder reaction
of the trazine ring with tributylstannylacetylene
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
to form the pyridine ring.
The BTBPs are related to the BTPs, the BTPs are the bitriazinyl 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
which was done during the PARTNEW EU funded project on advanced nuclear reprocessing
, 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 trinitrate complexes of most of the lanthanides have been characterised by X-ray
crystallography
, 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 nitrogen
s form an equatorial plane and two acetonitrile
molecules occupy the two axial
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
complexes of uranium.
In recent years the BTBPs have been investigated as reagents for the selective extraction of post-plutonium
metals such as americium
from nitric acid
solutions containing large amounts of lanthanide
s. Already one of the BTBPs has been shown to be able to selectively extract the americium and curium
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.
Ligand
In coordination chemistry, a ligand is an ion or molecule that binds to a central metal atom to form a coordination complex. The bonding between metal and ligand generally involves formal donation of one or more of the ligand's electron pairs. The nature of metal-ligand bonding can range from...
s similar in shape to quaterpyridine. The BTBPs are made by the reaction of hydrazine
Hydrazine
Hydrazine is an inorganic compound with the formula N2H4. It is a colourless flammable liquid with an ammonia-like odor. Hydrazine is highly toxic and dangerously unstable unless handled in solution. Approximately 260,000 tons are manufactured annually...
and a 1,2-diketone (such as hexane-3,4-dione) with 6,6'-dicyano-2,2'-bipyridine. The dicyanobipy can be made by reacting 2,2'-bipy with hydrogen peroxide
Hydrogen peroxide
Hydrogen peroxide is the simplest peroxide and an oxidizer. Hydrogen peroxide is a clear liquid, slightly more viscous than water. In dilute solution, it appears colorless. With its oxidizing properties, hydrogen peroxide is often used as a bleach or cleaning agent...
in acetic acid
Acetic acid
Acetic acid is an organic compound with the chemical formula CH3CO2H . It is a colourless liquid that when undiluted is also called glacial acetic acid. Acetic acid is the main component of vinegar , and has a distinctive sour taste and pungent smell...
, (followed by the addition of acetone
Acetone
Acetone is the organic compound with the formula 2CO, a colorless, mobile, flammable liquid, the simplest example of the ketones.Acetone is miscible with water and serves as an important solvent in its own right, typically as the solvent of choice for cleaning purposes in the laboratory...
) 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
Potassium cyanide is an inorganic compound with the formula KCN. This colorless crystalline compound, similar in appearance to sugar, is highly soluble in water. Most KCN is used in gold mining, organic synthesis, and electroplating. Smaller applications include jewelry for chemical gilding and...
and benzoyl chloride
Benzoyl chloride
Benzoyl chloride, also known as benzenecarbonyl chloride, is an organochlorine compound with the formula C6H5COCl. It is a colourless, fuming liquid with an irritating odour...
in a mixture of water
Water
Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...
and THF
Tetrahydrofuran
Tetrahydrofuran is a colorless, water-miscible organic liquid with low viscosity at standard temperature and pressure. This heterocyclic compound has the chemical formula 4O. As one of the most polar ethers with a wide liquid range, it is a useful solvent. Its main use, however, is as a precursor...
.
The BTBPs were first reported as synthetic intermidates in the synthesis of quaterpyridines by a Diels-Alder reaction
Diels-Alder reaction
The Diels–Alder reaction is an organic chemical reaction between a conjugated diene and a substituted alkene, commonly termed the dienophile, to form a substituted cyclohexene system. The reaction can proceed even if some of the atoms in the newly formed ring are not carbon...
of the trazine ring with tributylstannylacetylene
Acetylene
Acetylene is the chemical compound with the formula C2H2. 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 pure form and thus is usually handled as a solution.As an alkyne, acetylene is unsaturated because...
or norbornadiene
Norbornadiene
Norbornadiene is an organic compound. This bicyclic hydrocarbon is the most stable diolefin derived from the norbornane and norbornene. Norbornadiene is primarily of interest as a ligand in homogeneous catalysis, but it has been heavily studied due to its high reactivity and distinctive...
, after the Diels-Alder reaction a series of other reactions cause the adjunct to lose a molecule of nitrogen
Nitrogen
Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless, and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere...
and a molecule of cyclopentadiene
Cyclopentadiene
Cyclopentadiene is an organic compound with the formula C5H6. This colorless liquid has a strong and unpleasant odor. At room temperature, this cyclic diene dimerizes over the course of hours to give dicyclopentadiene via a Diels–Alder reaction...
to form the pyridine ring.
The BTBPs are related to the BTPs, the BTPs are the bitriazinyl 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
Reading, Berkshire
Reading is a large town and unitary authority area in England. It is located in the Thames Valley at the confluence of the River Thames and River Kennet, and on both the Great Western Main Line railway and the M4 motorway, some west of London....
in Berkshire
Berkshire
Berkshire is a historic county in the South of England. It is also often referred to as the Royal County of Berkshire because of the presence of the royal residence of Windsor Castle in the county; this usage, which dates to the 19th century at least, was recognised by the Queen in 1957, and...
which was done during the PARTNEW EU funded project on advanced nuclear reprocessing
Nuclear reprocessing
Nuclear reprocessing technology was developed to chemically separate and recover fissionable plutonium from irradiated nuclear fuel. Reprocessing serves multiple purposes, whose relative importance has changed over time. Originally reprocessing was used solely to extract plutonium for producing...
, 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 trinitrate complexes of most of the lanthanides have been characterised by X-ray
X-ray
X-radiation is a form of electromagnetic radiation. X-rays have a wavelength in the range of 0.01 to 10 nanometers, corresponding to frequencies in the range 30 petahertz to 30 exahertz and energies in the range 120 eV to 120 keV. They are shorter in wavelength than UV rays and longer than gamma...
crystallography
Crystallography
Crystallography is the experimental science of the arrangement of atoms in solids. The word "crystallography" derives from the Greek words crystallon = cold drop / frozen drop, with its meaning extending to all solids with some degree of transparency, and grapho = write.Before the development of...
, with a smaller metal such as nickel
Nickel
Nickel is a chemical element with the chemical symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel belongs to the transition metals and is hard and ductile...
the BTBPs are may bind with three nitrogens in some complexes. The perchlorate
Perchlorate
Perchlorates are the salts derived from perchloric acid . They occur both naturally and through manufacturing. They have been used as a medicine for more than 50 years to treat thyroid gland disorders. They are used extensively within the pyrotechnics industry, and ammonium perchlorate is also a...
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 nitrogen
Nitrogen
Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless, and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere...
s form an equatorial plane and two acetonitrile
Acetonitrile
Acetonitrile is the chemical compound with formula . This colourless liquid is the simplest organic nitrile. It is produced mainly as a byproduct of acrylonitrile manufacture...
molecules occupy the two axial
Axial
Axial may mean:* Along the same line as an axis of rotation in geometry* A type of modal frame in music* One of several anatomical directions in an animal body* Axial age, the period from 800 to 200 BC in China, India and the western world...
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
Uranium
Uranium is a silvery-white metallic chemical element in the actinide series of the periodic table, with atomic number 92. It is assigned the chemical symbol U. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons...
(VI) binds to BTBP to form a 1:1 complex, where the axial sites are occupied with the uranyl
Uranyl
The uranyl ion is an oxycation of uranium in the oxidation state +6, with the chemical formula [UO2]2+. It has a linear structure with short U-O bonds, indicative of the presence of multiple bonds between uranium and oxygen. Four or more ligands are bound to the uranyl ion in an equatorial plane...
oxygen atoms. The BTBPs are also able to bind to cyclopentadienyl
Cyclopentadienyl
In organic chemistry, cyclopentadienyl is a cyclic group of atoms with the formula C5H5. Cyclopentadienyl are closely related to cyclopentadiene. Cyclopentadienyl have five carbon atoms bonded together in a pentagonal planar ring, all five of which are bonded to individual hydrogen atoms...
complexes of uranium.
In recent years the BTBPs have been investigated as reagents for the selective extraction of post-plutonium
Plutonium
Plutonium is a transuranic radioactive chemical element with the chemical symbol Pu and atomic number 94. It is an actinide metal of silvery-gray appearance that tarnishes when exposed to air, forming a dull coating when oxidized. The element normally exhibits six allotropes and four oxidation...
metals such as americium
Americium
Americium is a synthetic element that has the symbol Am and atomic number 95. This transuranic element of the actinide series is located in the periodic table below the lanthanide element europium, and thus by analogy was named after another continent, America.Americium was first produced in 1944...
from nitric acid
Nitric acid
Nitric acid , also known as aqua fortis and spirit of nitre, is a highly corrosive and toxic strong acid.Colorless when pure, older samples tend to acquire a yellow cast due to the accumulation of oxides of nitrogen. If the solution contains more than 86% nitric acid, it is referred to as fuming...
solutions containing large amounts of lanthanide
Lanthanide
The lanthanide or lanthanoid series comprises the fifteen metallic chemical elements with atomic numbers 57 through 71, from lanthanum through lutetium...
s. Already one of the BTBPs has been shown to be able to selectively extract the americium and curium
Curium
Curium is a synthetic chemical element with the symbol Cm and atomic number 96. This radioactive transuranic element of the actinide series was named after Marie Skłodowska-Curie and her husband Pierre Curie. Curium was first intentionally produced and identified in summer 1944 by the group of...
from a genuine mixture formed from used MOX fuel
MOX fuel
Mixed oxide fuel, commonly referred to as MOX fuel, is nuclear fuel that contains more than one oxide of fissile material. MOX fuel contains plutonium blended with natural uranium, reprocessed uranium, or depleted uranium. MOX fuel is an alternative to the low-enriched uranium fuel used in the...
. The MOX fuel
MOX fuel
Mixed oxide fuel, commonly referred to as MOX fuel, is nuclear fuel that contains more than one oxide of fissile material. MOX fuel contains plutonium blended with natural uranium, reprocessed uranium, or depleted uranium. MOX fuel is an alternative to the low-enriched uranium fuel used in the...
was dissolved in nitric acid
Nitric acid
Nitric acid , also known as aqua fortis and spirit of nitre, is a highly corrosive and toxic strong acid.Colorless when pure, older samples tend to acquire a yellow cast due to the accumulation of oxides of nitrogen. If the solution contains more than 86% nitric acid, it is referred to as fuming...
, the bulk of the uranium
Uranium
Uranium is a silvery-white metallic chemical element in the actinide series of the periodic table, with atomic number 92. It is assigned the chemical symbol U. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons...
and plutonium
Plutonium
Plutonium is a transuranic radioactive chemical element with the chemical symbol Pu and atomic number 94. It is an actinide metal of silvery-gray appearance that tarnishes when exposed to air, forming a dull coating when oxidized. The element normally exhibits six allotropes and four oxidation...
were removed by means of a PUREX
PUREX
PUREX is an acronym standing for Plutonium - URanium EXtraction — de facto standard aqueous nuclear reprocessing method for the recovery of uranium and plutonium from used nuclear fuel. It is based on liquid-liquid extraction ion-exchange.The PUREX process was invented by Herbert H. Anderson and...
type extraction using tributyl phosphate in a hydrocarbon, the lanthanides and the remaining actinides were then separated from the aqueous residue (raffinate
Raffinate
Raffinating something is a technique used in metallurgy to remove impurities from liquid material. There are many different kinds of raffination, for example you can use vacuum to extract hydrogen from metals....
) by a diamide based extraction to give, after stripping, a mixture of trivalent actinides and lanthanides.