Organometallic Compounds - Examples, Preparation, Properties. Structure, FAQs
Organometallic compounds are a special and dynamic class of chemical compounds with at the minimum of one direct metal-carbon (M–C) bond. These compounds serve as a link between inorganic chemistry (compounds including metals) and organic chemistry (molecules based on carbon), and they are very useful in the feild of industrial operations, material science, medicines, and catalysis.
This Story also Contains
- Organometallic Compounds
- Classification of Organometallic Compounds
- Types And Examples of Organometallic Compounds
- Applications: Organometallic Compounds in Real Life
- Some Solved Examples
In this article, the topic of organometallic compounds are covered that are very important topics of chapter Coordination Compounds from the board exam point of view and also for the JEE Mains Exam, NEET Exam, and many other entrance exams like SRMJEE, BITSAT, WBJEE, BCECE, and more
Organometallic Compounds
Compounds that contain at least one carbon-metal bond are called organometallic compounds. The metal-carbon bond changes from covalent to ionic and even multicenter, which alters the reactivity and stability of the compounds.
Zeise, in 1830, prepared the first organometallic compound by the action of ethylene on a solution of Potassium chloroplatinate(II). Grignard reagent, $\text { RMgX, }$, is a familiar example of organometallic compounds where R is an alkyl group. Diethyl zinc $\left[\mathrm{Zn}\left(\mathrm{C}_2 \mathrm{H}_5\right)_2\right]$, lead tetraethyl $\left[\mathrm{Pb}\left(\mathrm{C}_2\mathrm{H}_5\right)_4\right]$, ferrocene $\left[\mathrm{Fe}\left(\mathrm{C}_5 \mathrm{H}_5\right)_2\right]$, dibenzene chromium $\left[\mathrm{Cr}\left(\mathrm{C}_6 \mathrm{H}_6\right)_2\right]$, metal carbonyls are other examples of organometallic compounds.
Classification of Organometallic Compounds
Sigma(σ) bonded Complexes:
These complexes contain a metal and carbon atom attached with a sigma bond e.g. Tetramethyl Tin, Trimethyl aluminum, etc.
Bonding in Trimethyl aluminum is shown below
Pi(π) Bonded Complexes:
These complexes contain a metal and carbon atom attached to a Pi Bond. e.g. Ferrocene, Dibenzene Chromium, etc. Bonding in Ferrocene and Dibenzene Chromium is shown below:
Complexes Containing Both σ and π Bonding Characteristics:
These complexes contain both σ as well as π bonding characteristics. e.g. Metal Carbonyls. The M−Cσ bond is formed by the donation of the lone pair of electrons of the carbonyl group into the vacant d orbital of metal while the M−Cπ bond is formed by the back donation of the lone pair of electrons from the metal into vacant antibonding π∗ molecular orbital of CO. This synergic bonding leads to the formation of stronger bonds and stable metal carbonyl complexes. The bonding in metal carbonyls is shown below:
Types And Examples of Organometallic Compounds
Organometallic compounds can be classified depending on the particular metal or the type of carbon-metal bond.
General Broad Categories Include:
- Main-Group Organometallics: They are compounds that react actively with alkali and alkaline earth metals to form organolithium and organomagnesium compounds. For instance, Grignard reagents are used in organic synthesis due to the fact that they can form carbon-carbon bonds.
- Transition Metal Organometallics: This class includes ferrocene and metal carbonyls. Ferrocene is an example of a metallocene; it contains a central iron atom sandwiched between two cyclopentadienyl anions.
- Apart from this, organometallics are also classified by functional groups and by the reactivity character of these groups. For example, organotin compounds are found in plastics, stabilizers, and biocides, while organocuprates are one of the dominating compounds in most nucleophilic substitution reactions.
Examples of tetra hepto ligands are Cycloheptatriene and cyclooctatetraene.
Examples of tetra hepto ligands are Cycloheptatriene and cyclooctatetraene.
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Applications: Organometallic Compounds in Real Life
The importance of organometallic compounds does not merely lie within the laboratories; they are also relevant in industries and real-life applications.
- Catalysis: Organometallic compounds act as catalysts in chemical reactions that more or less take place in the enhancement of reaction rate and selectivity. For example, organometallic complexes, such as Ziegler–Natta, are of paramount importance in the polymerization of alkenes, which in turn are used in making polyethylene and polypropylene. Pharmaceuticals: Organometallic compounds work as important mediums in the synthesis of many drugs in the pharmaceutical industry. They are important in that they can provide proper carbon-carbon bond formation so that highly complex organic molecules can be developed.
- Environmental Concerns: These compounds can either be of great utility or can be a great threat to health and the environment. An example is the very toxic compound methylmercury with one application which has caused very serious ecological and health problems.
- Semiconductors and Electronics: Organometallic compounds are used in the production of semiconductors and other electronic devices. For example, trimethylgallium for LED and solar cell MOCVD thin-film deposition.
- Organometallic compounds have applications both in academic research and in practical. Their special properties and reactivity make organometallic compounds powerful tools in the promotion of chemistry and technology.
Recommended video on (Organometallic Compound)
Some Solved Examples
Example 1
Question: Mn2(CO)10 is an organometallic compound due to the presence of:
1) Mn-C bond
2) Mn-Mn bond
3) Mn-O bond
4) C-O bond
Solution: Mn2(CO)10 is classified as an organometallic compound because it contains a Mn-C bond. Therefore, the correct answer is option (1).
Example 2
Question: The number of bridging CO ligands in [Mn2(CO)10] is __________.
1) 0
2)1
3)3
4)2
Solution: There are zero bridging CO ligands present in [Mn2(CO)10]. Thus, the answer is 0.
Example 3 Which of the following is not true for metal carbonyls?
1) The oxidation state of the metal in the carbonyls is generally zero
2) Metal carbonyls generally follow the Effective atomic number rule
3) Metal carbonyls have a bond order that is greater than 1 between the metal and the carbonyl carbon
4) (correct)$d \pi-p \pi$ overlap is observed in metal carbonyls
Solution
Metal carbonyls do not show $d \pi-p \pi$ overlapping.
The back donation takes place from the d orbital of the metal to the vacant $\pi^*$ molecular orbital of the carbonyl ligand.
All other statements are correct.
Hence, the answer is the option (4).
Example 4
Question: The number of complexes that will exhibit synergic bonding among [Cr(CO)6], [Mn(CO)5], and [Mn2(CO)10] is ________.
1) 3
2) 4
3) 8
4) 5
Solution: All three complexes are metal carbonyl complexes and exhibit synergic bonding. Hence, the answer is 3.
Example 5
Question: The oxidation states of iron atoms in compounds (A), (B), and (C), respectively, are x, y, and z. What is the sum of x, y, and z?
1) 6
2) 9
3) 4
4) 5
Solution: The sum of the oxidation states of iron atoms in compounds (A), (B), and (C) is 6. Therefore, the correct answer is 6.
Practice more questions from the link given below
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Frequently Asked Questions (FAQs)
A synergy where the metal donates electron density to ligand π* orbitals (e.g., in metal carbonyls like Ni(CO)₄), strengthening the M–L bond.
They are categorized by the metal’s position in the periodic table:
Main group (e.g., Grignard reagents, R-Mg-X).
Transition metal (e.g., Ferrocene, Pd(PPh₃)₄).
Lanthanide/Actinide (e.g., Cp₃Ln, used in polymerization).
They facilitate key reactions (e.g., C–C bond formation, hydrogenation) with high selectivity. Examples:
Wilkinson’s catalyst (RhCl(PPh₃)₃) for alkene hydrogenation.
Ziegler-Natta catalysts (Ti/Al) for polyolefin production.
Common applications of organometallics
Industrial: Synthesis of pharmaceuticals, plastics, and agrochemicals.
Materials: OLEDs, MOFs, and conductive polymers.
Medicine: Cisplatin (Pt-based anticancer drug), vitamin B₁₂ (Co complex)
Common methods:
Transmetallation (e.g., R₂Zn + HgCl₂ → R₂Hg + ZnCl₂).
Oxidative addition (e.g., Pd(0) + R-X → Pd(II)(R)(X)).
Metathesis (e.g., Grignard reactions).