Organozirconium Compound on:
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Organozirconium chemistry is the science of exploring the properties, structure, and reactivity of organozirconium compounds, which are
In addition to mixed Cp2Zr(CO)2, zirconium forms the binary carbonyl r(CO)6sup>2-.
Cationic hafnocene complexes,
organometallic compound
Organometallic chemistry is the study of organometallic compounds, chemical compounds containing at least one chemical bond between a carbon atom of an organic molecule and a metal, including alkali, alkaline earth, and transition metals, and ...
s containing chemical bond
A chemical bond is the association of atoms or ions to form molecules, crystals, and other structures. The bond may result from the electrostatic force between oppositely charged ions as in ionic bonds or through the sharing of electrons a ...
s between carbon
Carbon () is a chemical element; it has chemical symbol, symbol C and atomic number 6. It is nonmetallic and tetravalence, tetravalent—meaning that its atoms are able to form up to four covalent bonds due to its valence shell exhibiting 4 ...
and zirconium
Zirconium is a chemical element; it has Symbol (chemistry), symbol Zr and atomic number 40. First identified in 1789, isolated in impure form in 1824, and manufactured at scale by 1925, pure zirconium is a lustrous transition metal with a greyis ...
. Organozirconium compounds have been widely studied, in part because they are useful catalysts in Ziegler-Natta polymerization.
Comparison with organotitanium chemistry
Many organozirconium compounds have analogues onorganotitanium chemistry
Organotitanium chemistry is the science of organotitanium compounds describing their physical properties, synthesis, and reactions. Organotitanium compounds in organometallic chemistry contain carbon-titanium chemical bonds. They are reagents in or ...
. Zirconium(IV) is more resistant to reduction than titanium(IV) compounds, which often convert to Ti(III) derivatives. By the same token, Zr(II) is a particularly powerful reducing agent, forming robust dinitrogen complex
Transition metal dinitrogen complexes are coordination compounds that contain transition metals as ion centers the dinitrogen molecules (N2) as ligands.
Historical background
Transition metal complexes of N2 have been studied since 1965 when ...
es. Being a larger atom, zirconium forms complexes with higher coordination numbers, e.g. polymeric pZrCl3sub>n vs monomeric CpTiCl3 (Cp = C5H5).
History
Zirconocene dibromide was prepared in 1953 by a reaction of thecyclopentadienyl Cyclopentadienyl can refer to
* Cyclopentadienyl anion, or cyclopentadienide,
** Cyclopentadienyl ligand
* Cyclopentadienyl radical, •
* Cyclopentadienyl cation,
See also
* Pentadienyl
{{Chemistry index ...
magnesium bromide and zirconium(IV) chloride. In 1966, the dihydride Cp2ZrH2 was obtained by the reaction of Cp2Zr(BH4)2 with triethylamine
Triethylamine is the chemical compound with the formula N(CH2CH3)3, commonly abbreviated Et3N. Like triethanolamine and the tetraethylammonium ion, it is often abbreviated TEA. It is a colourless volatile liquid with a strong fishy odor remini ...
. In 1970, the related hydrochloride (now called Schwartz's reagent
Schwartz's reagent is the common name for the organozirconium compound with the formula (C5H5)2ZrHCl, sometimes called zirconocene hydrochloride or zirconocene chloride hydride, and is named after Jeffrey Schwartz, a chemistry professor at Princet ...
) was obtained by reduction of zirconacene dichloride (Cp2ZrCl2) with lithium aluminium hydride
Lithium aluminium hydride, commonly abbreviated to LAH, is an inorganic compound with the chemical formula or . It is a white solid, discovered by Finholt, Bond and Schlesinger in 1947. This compound is used as a reducing agent in organic synthe ...
(or the related LiAlH(t-BuO)3). The development of organozirconium reagents was recognized by a Nobel Prize in Chemistry
The Nobel Prize in Chemistry () is awarded annually by the Royal Swedish Academy of Sciences to scientists in the various fields of chemistry. It is one of the five Nobel Prizes established by the will of Alfred Nobel in 1895, awarded for outst ...
to Ei-Ichi Negishi.
Zirconocene chemistry
The foremost applications of zirconocenes involve their use as catalysts for olefin polymerization.Schwartz's reagent
Schwartz's reagent is the common name for the organozirconium compound with the formula (C5H5)2ZrHCl, sometimes called zirconocene hydrochloride or zirconocene chloride hydride, and is named after Jeffrey Schwartz, a chemistry professor at Princet ...
( p2ZrHClsub>2) participates in hydrozirconation, which enjoys some use in organic synthesis
Organic synthesis is a branch of chemical synthesis concerned with the construction of organic compounds. Organic compounds are molecules consisting of combinations of covalently-linked hydrogen, carbon, oxygen, and nitrogen atoms. Within the gen ...
. Substrates for hydrozirconation
Schwartz's reagent is the common name for the organozirconium compound with the formula (C5H5)2ZrHCl, sometimes called zirconocene hydrochloride or zirconocene chloride hydride, and is named after Jeffrey Schwartz, a chemistry professor at Princeto ...
are alkene
In organic chemistry, an alkene, or olefin, is a hydrocarbon containing a carbon–carbon double bond. The double bond may be internal or at the terminal position. Terminal alkenes are also known as Alpha-olefin, α-olefins.
The Internationa ...
s and alkyne
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Acetylene
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\ce
\ce
Propyne
\ce
\ce
\ce
\ce
1-Butyne
In organic chemistry, an alkyne is an unsaturated hydrocarbon containing at least one carbon—carbon triple bond. The simplest acyclic alkynes with only one triple bond and n ...
s. Terminal alkynes give vinyl complexes. Secondary reactions are nucleophilic addition
In organic chemistry, a nucleophilic addition (AN) reaction is an addition reaction where a chemical compound with an electrophilic double or triple bond reacts with a nucleophile, such that the double or triple bond is broken. Nucleophilic addit ...
s, transmetalation Transmetalation (alt. spelling: transmetallation) is a type of organometallic reaction that involves the transfer of ligands from one metal to another. It has the general form:
:M1–R + M2–R′ → M1–R′ + M2–R
where R and R′ can be, but ...
s, conjugate addition
Nucleophilic conjugate addition is a type of organic reaction. Ordinary nucleophilic additions or 1,2-nucleophilic additions deal mostly with additions to carbonyl compounds. Simple alkene compounds do not show 1,2 reactivity due to lack of polar ...
s, coupling reaction
In organic chemistry, a coupling reaction is a type of reaction in which two reactant molecules are bonded together. Such reactions often require the aid of a metal catalyst. In one important reaction type, a main group organometallic compound o ...
s, carbonylation
In chemistry, carbonylation refers to reactions that introduce carbon monoxide (CO) into organic and inorganic substrates. Carbon monoxide is abundantly available and conveniently reactive, so it is widely used as a reactant in industrial chemis ...
, and halogenation
In chemistry, halogenation is a chemical reaction which introduces one or more halogens into a chemical compound. Halide-containing compounds are pervasive, making this type of transformation important, e.g. in the production of polymers, drug ...
.
Extensive chemistry has also been demonstrated from decamethylzirconocene dichloride
Decamethylzirconocene dichloride is an organozirconium compound with the formula Cp*2ZrCl2 (where Cp* is C5(CH3)5, derived from pentamethylcyclopentadiene). It is a pale yellow, moisture sensitive solid that is soluble in nonpolar organic solven ...
, Cp*2ZrCl2. Well-studied derivatives include Cp*2ZrH2, p*2Zrsub>2(N2)3, Cp*2Zr(CO)2, and Cp*2Zr(CH3)2.
Zirconocene dichloride can be used to cyclise enynes and dienes to give cyclic or bicyclic aliphatic systems.
:
Alkyl and CO complexes
The simplest organozirconium compounds are thehomoleptic
In inorganic chemistry, a homoleptic chemical compound is a metal compound with all ligands identical. The term uses the " homo-" prefix to indicate that something is the same for all. Any metal species which has more than one type of ligand is he ...
alkyls. Salts of r(CH3)6sup>2- are known. Tetrabenzylzirconium is a precursor to many catalysts for olefin polymerization. It can be converted to mixed alkyl
In organic chemistry, an alkyl group is an alkane missing one hydrogen.
The term ''alkyl'' is intentionally unspecific to include many possible substitutions.
An acyclic alkyl has the general formula of . A cycloalkyl group is derived from a cy ...
, alkoxy
In chemistry, the alkoxy group is an alkyl group which is Single bond, singularly bonded to oxygen; thus . Denoted usually with apostrophe('). The range of alkoxy groups is vast, the simplest being methoxy (). An ethoxy group () is found in the ...
, and halide derivatives, Zr(CH2C6H5)3X (X = CH3, OC2H5, Cl).
In addition to mixed Cp2Zr(CO)2, zirconium forms the binary carbonyl r(CO)6sup>2-.
Organohafnium chemistry
Organohafnium compounds behave nearly identically to organozirconium compounds, as hafnium is just below zirconium on the periodic table. Many Hf analogues of Zr compounds are known, including bis(cyclopentadienyl)hafnium(IV) dichloride, bis(cyclopentadienyl)hafnium(IV) dihydride, and dimethylbis(cyclopentadienyl)hafnium(IV).
Cationic hafnocene complexes, 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, are used on an industrial scale for the polymerization
In polymer chemistry, polymerization (American English), or polymerisation (British English), is a process of reacting monomer molecules together in a chemical reaction to form polymer chains or three-dimensional networks. There are many fo ...
of alkenes.
Additional reading
* *References
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