Problem 18 - A Complete Resource Book in Chemistry for JEE Main

Question

Which of the following is not considered as an oganometallic compound? (a) ferrocene (b) cisplatin (c) Grignard's reagent (d) zeise's salt

Step-by-Step Solution

Answer

Cisplatin is not considered an organometallic compound.

Step 1: Identifying Organometallic Compounds

Organometallic compounds are defined by the presence of a metal-to-carbon bond, where the carbon belongs to an organic group. Let's identify whether each of the given options meets this criterion.

Step 2: Analyzing Ferrocene

Ferrocene is a well-known organometallic compound with iron (Fe) sandwiched between two cyclopentadienyl anions. Thus, it contains metal (Fe) to carbon (C) bonds.

Step 3: Assessing Cisplatin

Cisplatin is a platinum-containing compound primarily used as an anticancer drug. It has the formula Pt(NH₃)₂Cl₂ and contains Pt-N and Pt-Cl bonds but not any metal-to-carbon bonds, so it is not an organometallic compound.

Step 4: Evaluating Grignard's Reagent

Grignard's reagent has the general formula RMgX, where R is an organic group (typically an alkyl or aryl group). It contains a metal (Mg) to carbon (C) bond, making it organometallic.

Step 5: Reviewing Zeise's Salt

Zeise's salt is a complex with an ethylene group coordinated to a platinum metal center, thus containing metal-to-carbon bonding. Therefore, it is considered an organometallic compound.

Key Concepts

Metal-Carbon Bonds

In the realm of chemistry, metal-carbon bonds are a defining feature of organometallic compounds. These bonds signify a direct link between a metal and a carbon atom within an organic group. Organometallic chemistry, therefore, blends elements of traditional inorganic and organic chemistry. Here are some key characteristics of metal-carbon bonds:

• The metal in these bonds can be a transition metal or any other metal from the periodic table.
• Carbon can be part of various organic groups, which means that the nature of the bond can vary widely, affecting the properties and reactivity of the compound.
• Organometallic compounds often act as catalysts in industrial processes, such as the polymerization of alkenes.

Studying metal-carbon bonds is crucial because they provide unique insights into reactivity patterns and bonding in both organic and inorganic chemistry realms.

Cisplatin

Cisplatin is an intriguing chemical compound used largely in medicine as a chemotherapy drug. Despite sharing some structural similarities with organometallic compounds, it is not one.

• Composition: Cisplatin has the chemical formula Pt(NH₃)₂Cl₂. It comprises a platinum ion bonded to two ammine (NH₃) groups and two chloride ions (Cl⁻).
• Bonding: The compound primarily includes platinum-nitrogen and platinum-chlorine bonds. Notably, it lacks any metal-carbon bond, removing it from the organometallic category.
• Medical Use: Medicinally, Cisplatin interrupts cell division, making it effective against certain cancers, particularly those of the bladder, ovaries, and testicles.

Cisplatin's activity in the body exemplifies the interplay between chemical structure and biological function, underlining why it's a staple in cancer treatment.

Grignard Reagent

The Grignard reagent is a cornerstone in organometallic chemistry for synthetic applications. Named after Victor Grignard, who discovered it, this reagent has the formula RMgX, where "R" is a hydrocarbon group and "X" is a halogen.

• Synthesis: Grignard reagents are formed through the reaction of an alkyl or aryl halide with magnesium metal.
• Characterization: The presence of a metal-carbon bond (Mg-C) is what classifies these reagents as organometallic.
• Reactivity: They are nucleophilic, which means they can attack electrophilic carbon atoms, widely making them valuable intermediates in the preparation of alcohols, carboxylic acids, and other carbon-based compounds.

The Grignard reaction serves as an essential tool in organic synthesis, showcasing the versatile applications of organometallic chemistry.

Zeise's Salt

Zeise's Salt is a fascinating organometallic compound known for its unique bonding structure. Identified as potassium trichloro(ethylene)platinate(II), it presents a significant example in platinum complexes.

• Structure: In Zeise's salt, the ethylene group coordinates with a platinum metal center, resulting in a distinctive metal-carbon bond.
• Discovery: This compound was one of the earliest known examples of an olefin complex, illustrating the concept of π-bonding between metals and hydrocarbons.
• Influence: The understanding of such bonds has furthered insights into catalyst design, particularly in refining and petrochemical industries.

Zeise's Salt not only exemplifies fundamental principles of organometallic chemistry but also highlights significant progress in the development of coordination chemistry.