Organic compounds formed by the direct bonding of metal atoms and carbon atoms are called organometallic compounds, i.e. compounds containing M-C bonds[1]。Such as methyl potassium (CHthreeK）、Butyl lithium (CfourHnineLi), etc.
However, the organic matter with O, S, N and other elements as metal coordination atoms does not belong toOrganometallic compoundIt is an inorganic complex and belongs to the research field of coordination chemistry.[2]
andcarbon monoxideLigandsCarbonyl metal（Mx(CO)y）Although it is an inorganic complex, it is closely related to other organometallic compounds and has similar properties, so it also belongs to organometallic compounds.[2]
Cyanide (CN-）As ligand complexes, metal carbides, etc., although they also contain M-C bonds, are quite different from organometallic compounds in nature, so they do not belong to organometallic compounds.[2]
According to《IUPAC Naming Principles of Organic Chemistry》The provisions of,Usually contains metal of 1-12 familiesOrganometallic compoundIt belongs to inorganic substance;It does not contain these elements and can be named according to IUPAC Organic Chemistry Naming PrinciplesOrganometallic compoundsIt belongs to organic matter。[1]
Organometallic compounds are widely used in production and life.For example, when preparingPolymer compoundAlkyl aluminum is commonly used ascatalyzerIn organic synthesis, organometallic compounds can provideCarbonium anion, free radicals andCabbeenTherefore, organometallic compounds are very useful synthetic reagents.In recent years, many organometallic compoundsbiological activityWith the popularization and application of research, the research and application of biological activities and pharmacological effects of organometallic compounds have been increasingly in-depth developed.Therefore, it is necessary to master some basic knowledge of organometallic compounds.
The metal ions existing in the organism often use atoms with high electronegativity such as nitrogen and oxygen to passCoordination bondIt combines with organic molecules.These compounds are not organometallic compounds.However, the study of C-metal ligands formed by transition metals and organic compounds makes organometallic compounds and organic compoundsMetal complexThe distance between them is shrinking.The metal ions in enzyme molecules are very important for maintaining the conformation of biological macromolecules and enzyme catalytic function.For example, zinc ion iscarbonic anhydraseComponents of,hemoglobinThe function of carrying oxygen in vivo is also achieved through the reversible combination of iron ion and oxygen in heme.[3]
Compound naming
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The most common way to name organometallic compounds is to add the name of metal after the organic group.
When the metal atom in the organometallic compound molecule is connected with other atoms besides the organic group, it can be named as an inorganic salt with organic group.
1. The first main group is prepared by the reaction of active metals with halogenated hydrocarbons, and the corresponding organometallic compounds can be prepared by the reaction of magnesium, zinc and other active metals with halogenated hydrocarbons.For example:
Reaction equation
2. ByGrignard reagentPreparation Grignard reagent reacts with anhydrous metal halides, which can be used to prepare organometallic compounds of less active metals.
For example:
Reaction equation
3. The reaction of alkyl lithium with less active metal halides can be used to prepare another organometallic compound.For example:
Reaction equation
General nature
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The properties of organometallic compounds mainly depend on the chemical bonds formed between metal atoms and carbon atoms.Due to the different activity of metals, the properties of chemical bonds formed between metal atoms and carbon atoms are different.Therefore, the properties of organometallization cannot be generalized.The properties of organometallic compounds are as follows:
Properties of ionic compounds
Organometallic compounds containing active metals, due to the strong polarity of carbon metal bond, haveIonic compoundThe nature of.
For example: methyl potassium (CHthreeK)，The C-K bond in the molecule mainly shows the characteristics of ionic bond.The compound is a solid at room temperature and has many properties formed by methyl anion and potassium cation, especially the property of very active free carbon anion.For example, it can burn in the air, easily combine with moisture, and react violently with acid substances or oxidants.
For example: Dimethylmercury [(CHthree)twoHg]，The C-Hg bond in the molecule mainly shows the nature of covalent bond.The compound is a colorless liquid at room temperature, soluble in most organic solvents, does not react with water, oxygen and most inorganic acids at room temperature, and can be decomposed into mercury and methyl free radicals under heating or light conditions, and methyl free radicals are immediately dimerized to ethane.From the reaction of thermal decomposition to free radicals, dimethylmercury is an organic compound, and C-Hg bond has the property of covalent bond.
lewis acidic
Organic metal compounds formed by magnesium, aluminum, gallium, indium and other metals. The carbon metal bond has the property of polar covalent bond.When aluminum, gallium, etcMain family elementsIn the organic metal compound molecules formed, the metal atoms are not surrounded by 8-electron saturated stable structures, and have the tendency to form dimers or accept electron pairs to achieve saturated stable structures.
For example:Trimethyl aluminumIt often exists in the form of dimer,Trimethyl galliumIt can form 1:1 complexes with Lewis bases (such as trimethylamine, ether, etc.).This shows that the organometallic compounds formed by the third main group elements are the electron layer structures that share lone pair electrons as electron donor atoms of Lewis acid and Lewis base to reach saturation.
Common compounds
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There are many kinds of organometallic compounds, which are widely used.With the development of industry and scientific progress, the research and use of organometallic compounds will be more in-depth and extensive. Here are some commonly used organometallic compounds.[3]
Buli
Organic lithium compoundsIt is an important alkali metal organic compound, which has important value in organic synthesis and the preparation of polymer compounds.Butyl lithium is widely used.
Butyl lithium is soluble in benzene or cyclohexane, its properties are similar to Grignard reagent, and it is more active than Grignard reagent.Some useful reactions can occur.
1. React with hydrocarbon
Butyl lithium reacts with hydrocarbons containing more active hydrogen atoms, and lithium atoms replace the active hydrogen atoms to generate new organic lithium compounds and n-butane.
Reaction of butyl lithium with hydrocarbon
The above reaction can be regarded as the process of removing a proton from the substrate to obtain a new carbonium anion by lithium salt with strong alkaline carbonium anion.This reaction represents a method for preparing more complex organic lithium compounds from simple organic lithium compounds, which is called hydrocarbon metallization.
Butyl lithium reacts with carbon dioxide to form lithium valerate, and lithium valerate reacts with butyl lithium, and the product is hydrolyzed to obtain ketone.
Reaction equation
3. Addition reaction with olefins
Butyl lithium reacts with olefins to form carbon carbon double bond addition.If it is added to asymmetric alkenes, lithium atoms are added to double bonded carbon atoms with less hydrogenogen.For example:
Addition reaction with olefins
4. Catalysts for synthesis of polymer compounds
Butyl lithium and other organic lithium compounds can be used as catalysts for the synthesis of polymer compounds from olefins.For example, ethylene is polymerized into polyethylene, and isoprene is polymerized intoPolyisoprene（Synthetic natural rubber）Etc.
Dimethyl zinc
The general formula of organic zinc compound is RtwoZn，The molecules all contain linear C-Zn-C skeletons.
Dimethyl zinc[(CHthree)twoZn] is a volatile liquid at room temperature, with a boiling point of 44 ℃, and its chemical properties are not as active as organic lithium compounds.
Dimethylzinc is often used as a catalyst for polymerization, such as initiator for various olefin monomers and carbonylation polymerization, and also as Ziegler NattaComposite catalystComponents of.When organic zinc was used as initiator, the polymerization rate and molecular weight of the polymer varied with the composition of the composite catalyst.
Triethyl aluminum
Organic aluminum compoundsThere are many kinds, which can be divided into three categories according to the number of alkyl groups connected to aluminum atoms:
RthreeAl、RtwoAIZ、RAIZtwo；
Where R represents hydrocarbon radical, Z represents HF、Cl、Br、I、OR、SR、NHtwo、NHR、PRtwoEtc.
Triethyl aluminum is a colorless liquid, which can be rapidly oxidized or even spontaneously ignited when contacting with air. When encountering water, it will react strongly with water to generate aluminum hydroxide and ethane, and generate a lot of heat. Therefore, triethylaluminum is usually stored in hydrocarbon solvents, so special care should be taken when using it.Due to the active chemical properties and poor thermal stability of triethyl aluminum, it is difficult to obtain its pure product.Triethyl aluminum is widely used in industry, such as triethylaluminum andTitanium tetrachlorideThe composite catalyst is called Ziegler sodium tower catalyst, which can polymerize ethylene under normal pressure and also enable directional polymerization of propylene. Therefore, triethylaluminum is produced in large quantities and widely used in industry.
