Organosilver chemistry
Encyclopedia
Organosilver chemistry in chemistry
is the study of organometallic compounds containing a carbon
to silver
chemical bond
and the study of silver as catalyst in organic reaction
s. In the group 11 element
s silver is the element below copper. The chemistries have much in common but organosilver catalysis is much less common (mostly academic study) than organocopper chemistry obviously due to the price of the metal but also due to poor thermal stability of the organocompounds. The oxidation state
for silver in organosilver compounds in exclusively +1 with the notable exception of Ag(III) in the trifluoromethyl silver anion Ag(CF3)4- because of the electron-withdrawing effect of the trifluoromethyl
groups. Poor thermal stability is reflected in decomposition temperatures of AgMe (-50°C) versus CuMe (-15°C) and PhAg (74°C) vs PhCu (100°C)
The first attempts in organosilver were recorded by Buckton in 1859 and by J. A. Wanklyn & L. Carius
in 1861 . The first synthesis of an organosilver compound (methyl silver) was described by Semerano and Riccoboni in 1941.
Alternatively, diphenylzinc
may be used:
The silver mesitylene
adduct is a tetramer. it can be formed from silver chloride
and the Grignard reagent:
Silver forms stable complexes with ylide
s such as triphenylphosphonium methylide:
The C-Ag bond is stabilized by perfluoroalkyl ligands:
Alkenylsilver compounds are also more stable than their alkylsilver counterparts. Vinylsilver can be obtained by reaction of silver nitrate with tetravinyllead:
Silver-NHC complexes
are easily prepared, and are commonly used to prepare other NHC complexes by displacing labile ligands. For example, the reaction of the bis(NHC)silver(I) complex with bis(acetonitrile)palladium dichloride or chlorido(dimethyl sulfide)gold(I):
. Silver nitrate
is used to separate out alkenes as the η2-alkene complex. Silver is also present in other carbon-carbon bond
skeletal rearrangements such as the quadricyclane
to norbornadiene
rearrangement, the cubane
to cuneane
rearrangement and the rearrangement of the cyclobutadiene dimer to cyclooctatetraene
.
Chemistry
Chemistry is the science of matter, especially its chemical reactions, but also its composition, structure and properties. Chemistry is concerned with atoms and their interactions with other atoms, and particularly with the properties of chemical bonds....
is the study of organometallic compounds containing a carbon
Carbon
Carbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds...
to silver
Silver
Silver is a metallic chemical element with the chemical symbol Ag and atomic number 47. A soft, white, lustrous transition metal, it has the highest electrical conductivity of any element and the highest thermal conductivity of any metal...
chemical bond
Chemical bond
A chemical bond is an attraction between atoms that allows the formation of chemical substances that contain two or more atoms. The bond is caused by the electromagnetic force attraction between opposite charges, either between electrons and nuclei, or as the result of a dipole attraction...
and the study of silver as catalyst in organic reaction
Organic reaction
Organic reactions are chemical reactions involving organic compounds. The basic organic chemistry reaction types are addition reactions, elimination reactions, substitution reactions, pericyclic reactions, rearrangement reactions, photochemical reactions and redox reactions. In organic synthesis,...
s. In the group 11 element
Group 11 element
A Group 11 element is one in the series of elements in group 11 in the periodic table, consisting of transition metals which are the traditional coinage metals of copper , silver , and gold...
s silver is the element below copper. The chemistries have much in common but organosilver catalysis is much less common (mostly academic study) than organocopper chemistry obviously due to the price of the metal but also due to poor thermal stability of the organocompounds. The oxidation state
Oxidation state
In chemistry, the oxidation state is an indicator of the degree of oxidation of an atom in a chemical compound. The formal oxidation state is the hypothetical charge that an atom would have if all bonds to atoms of different elements were 100% ionic. Oxidation states are typically represented by...
for silver in organosilver compounds in exclusively +1 with the notable exception of Ag(III) in the trifluoromethyl silver anion Ag(CF3)4- because of the electron-withdrawing effect of the trifluoromethyl
Trifluoromethyl
Trifluoromethyl is a functional group in organofluorines that has the formula -CF3. The naming of is group is derived from the methyl group , by replacing each hydrogen atom by a fluorine atom. The trifluomethyl group has a significant electronegativity that is often described as being...
groups. Poor thermal stability is reflected in decomposition temperatures of AgMe (-50°C) versus CuMe (-15°C) and PhAg (74°C) vs PhCu (100°C)
The first attempts in organosilver were recorded by Buckton in 1859 and by J. A. Wanklyn & L. Carius
Georg Ludwig Carius
Georg Ludwig Carius was a German chemist born in Barbis. He studied under Friedrich Wöhler and was assistant to Robert Bunsen for 6 years. He was Director of the Marburger Chemical Institute of Philipps University of Marburg from 1865...
in 1861 . The first synthesis of an organosilver compound (methyl silver) was described by Semerano and Riccoboni in 1941.
Compounds
Phenylsilver can be obtained by reaction of silver nitrate with an trialkylphenyllead compound:- AgNO3 + R3PhPb → PhAg
Alternatively, diphenylzinc
Diphenylzinc
Diphenylzinc is an organozinc compound. It is commonly used as the synthetic equivalent of a a Ph− synthon. Solvent-free diphenylzinc exists as dimeric PhZn2ZnPh molecules in solid state....
may be used:
- Ph2Zn + AgNO3 → PhAg + PhZnNO3
The silver mesitylene
Mesitylene
Mesitylene or 1,3,5-trimethylbenzene is an aromatic hydrocarbon with three methyl substituents attached to the benzene ring. It is prepared by distillation of acetone with sulfuric acid or by trimerization of propyne in sulfuric acid, which, in both cases, acts as a catalyst and dehydrating agent....
adduct is a tetramer. it can be formed from silver chloride
Silver chloride
Silver chloride is a chemical compound with the chemical formula AgCl. This white crystalline solid is well known for its low solubility in water . Upon illumination or heating, silver chloride converts to silver , which is signalled by greyish or purplish coloration to some samples...
and the Grignard reagent:
- AgCl + MesMgBr → Ag4(Mes)4 + MgClBr
Silver forms stable complexes with ylide
Ylide
An ylide or ylid is a neutral dipolar molecule containing a formally negatively charged atom directly attached to a hetero atom with a formal positive charge , and in which both atoms have full octets of electrons. Ylides are thus 1,2-dipolar compounds...
s such as triphenylphosphonium methylide:
- AgCl + Ph3P=CH2 → AgCl(Ph3P=CH2)
The C-Ag bond is stabilized by perfluoroalkyl ligands:
- AgF + CF2=CF(CF3) → AgCF(CF3)2
Alkenylsilver compounds are also more stable than their alkylsilver counterparts. Vinylsilver can be obtained by reaction of silver nitrate with tetravinyllead:
- AgNO3 + (CH2=CH)4Pb → (CH2=CH)Ag + (CH2=CH)3PbNO3
Silver-NHC complexes
Transition metal carbene complex
A transition metal carbene complex is a organometallic compound featuring a divalent organic ligand. The divalent organic ligand coordinated to the metal center is called a carbene. Carbene complexes for almost all transition metals have been reported. Many methods for synthesizing them and...
are easily prepared, and are commonly used to prepare other NHC complexes by displacing labile ligands. For example, the reaction of the bis(NHC)silver(I) complex with bis(acetonitrile)palladium dichloride or chlorido(dimethyl sulfide)gold(I):
Catalysis
In catalysis silver is active as silver oxide in the Wolff rearrangementWolff rearrangement
The Wolff rearrangement is a rearrangement reaction converting a α-diazo-ketone into a ketene. This reaction was first reported by Ludwig Wolff in 1912....
. Silver nitrate
Silver nitrate
Silver nitrate is an inorganic compound with chemical formula . This compound is a versatile precursor to many other silver compounds, such as those used in photography. It is far less sensitive to light than the halides...
is used to separate out alkenes as the η2-alkene complex. Silver is also present in other carbon-carbon bond
Carbon-carbon bond
A carbon–carbon bond is a covalent bond between two carbon atoms. The most common form is the single bond: a bond composed of two electrons, one from each of the two atoms. The carbon–carbon single bond is a sigma bond and is said to be formed between one hybridized orbital from each...
skeletal rearrangements such as the quadricyclane
Quadricyclane
Quadricyclane is a strained, multi-cyclic hydrocarbon with potential uses as an additive for rocket propellants as well in solar energy conversion. These uses are limited, however, by the molecule's decomposition at relatively low temperatures .-Structure and properties:Quadricyclane is a highly...
to 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...
rearrangement, the cubane
Cubane
Cubane is a synthetic hydrocarbon molecule that consists of eight carbon atoms arranged at the corners of a cube, with one hydrogen atom attached to each carbon atom. A solid crystalline substance, cubane is one of the Platonic hydrocarbons. It was first synthesized in 1964 by Philip Eaton, a...
to cuneane
Cuneane
Cuneane is a saturated hydrocarbon. Its name is derived from the Latin “cuneus”, meaning a wedge. Cuneane may be produced from cubane by metal-ion-catalyzed σ-bond rearrangement. Similar reactions are known for homocubane and bishomocubane...
rearrangement and the rearrangement of the cyclobutadiene dimer to cyclooctatetraene
Cyclooctatetraene
1,3,5,7-Cyclooctatetraene is an unsaturated derivative of cyclooctane, with the formula C8H8. It is also known as [8]annulene. This polyunsaturated hydrocarbon is a colorless to light yellow flammable liquid at room temperature...
.
See also
- Chemical bonds of carbon with other elements in the periodic table: