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Metal Carbonyls Organometallics

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What are Metal Carbonyls?

Metal Carbonyls can be defined as compounds that are volatile and have low melting points. They are made from the compound of Mx(Co)y that decomposes into carbon monoxide and metal on heating. They can be toxic when in contact with skin. They can also be toxic if inhaled or ingested due to their property of carbonylate haemoglobin which converts it into carboxyhemoglobin that further prevents the binding of oxygen in the blood cells. Furthermore, in a metal carbonyl, both characters, σ, and π, are possessed by the metal-carbon bond. This bond is further strengthened by the synergic effect produced by the metal-ligand bond. 


Metal Carbonyls and Their Structure

When learning about metal carbonyls, it is important to study their structure as well. One of the unique properties of metal carbonyls is that they exist in two types of bonding. The first kind exists when there is a donation of electrons by the carbonyl molecules to the vacant orbitals of the metal, thereby forming a metal-carbon σ bond.


The second type is when there is a donation of a pair of electrons from a filled d orbital metal into the vacant anti bonding π* orbital of a carbonyl ligand. This way a metal-carbon π bond is formed. The 18-electron rule is generally used in predicting the stability of metal carbonyls. According to this rule, the electrons are gained from the ligands by the metal atom to reach the nearest noble gas configuration.


What Are Metal Carbonyls Organometallics?

Metal Carbonyl Organometallics can be defined as compounds that consist of at least one metal-to-carbon bond. Moreover, the carbon in the metal-to-carbon bond is part of an organic group. The organometallic compounds play a major role in the development of the science of chemistry. 


An example of an organometallic compound is ferrocene in which an iron atom is in between two hydrocarbon rings. There are great variations amongst the physical and chemical properties of organometallic compounds. Most of them are solid, specifically those with ring-shaped hydrocarbon groups. 


Some organometallic compounds are present both in liquid and gaseous states. They can also be flammable, particularly the compounds of electropositive elements such as lithium, aluminium, and sodium. Major organometallic compounds are highly toxic and volatile. Some common examples of organometallics are Grignard Reagent - RMgX, Gilman Reagent - R2CuLi, Dimethylmagnesium - Me2Mg, Triethylborane - Et3B, Ferrocene, Cobaltocene. 


Properties of Metal Carbonyls Organometallics

The 18-electron rule followed by metal carbonyl is surprisingly not followed by metal carbonyls organometallics. Some other basic properties of metal carbonyl organometallics are specified below:

  • Organometallics are not soluble in water

  • Instead, they are soluble in ether

  • Metal Carbonyls Organometallics has a relatively low melting point

  • Another interesting property of organometallics is their electronegativity. While metals have a lower electronegativity of 20, the organometallic carbon compound has an electronegativity of 2.5.

  • Organometallic compounds are also highly reactive. That is the reason why they are generally kept in organic solvents.

Uses of Metal Carbonyl Organometallic

The discovery of organometallic compounds has led to their application in various fields. Some of the popular uses of organometallics are specified below:

  • The most common use of organometallic compounds is as a reagent.

  • Organoarsenic compounds are also used in the treatment of a common sexually transmitted disease called syphilis. 

  • Grignard reagent, which is a popular organometallic compound is used for various purposes such as in the synthesis of a secondary alcohol, aldehydes, etc. 

  • Another use of organometallic is as an additive

  • They are also useful for various industrial purposes. 

  • Cis-plastin, an organometallic compound, is used as an anticancer drug

  • For hydrogenation alkenes, Wilkison’s catalyst is used

FAQ (Frequently Asked Questions)

Q1. What are the Classifications of Organometallic Compound?

Ans. As specified in the article above, there are huge variations in the category of organometallic compounds. To simplify this range of variations, the metal carbonyls category of organometallics has been divided further. With the help of these classifications, it is easier to study the chemical and physical properties of organometallic compounds and thereby put them for applications as per their properties. The classifications for organometallics in specified below:

  • Main Group Organometallic Compound

  • Transition Metal Organometallic Compound

  • Lanthanide and Actinide Organometallic Compound

Q2.How to Define the Three Classifications of  Organometallic Compounds?

Ans. The classification of organometallic is in three categories. The first classification category is of the main group organometallic compounds. These compounds have s or p block element(s)  in them. Examples from the main group are Grignard Reagent, Cacodyl Oxide, Organoborane, etc. The second classification is of transition metal organometallic compound. 


In these the d-block element is present. Examples from this category are Gillmann’s Reagent, Collmann’s Reagent, Wilkison’s catalyst, etc. The last classification is that of Lanthanide and Actinide Organometallic compounds in which there is f-block metal/s present. Some of the common examples of Uranocene and Cyclopentadienides.