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

The compound not considered organometallic is (b) cisplatin.

Step 1: Understand Organometallic Compounds

Organometallic compounds are defined as compounds that feature bonds between a metal atom and carbon atoms from an organic group. The metal is often a transition metal.

Step 2: Analyze Each Option

- Ferrocene is a classic organometallic compound with iron (Fe) bonded to cyclopentadienyl rings (an organic group). - Cisplatin is a coordination complex of platinum (Pt) with ligands including ammonia and chloride ions, but no carbon-metal bond. - Grignard's reagent is typically formed as RMgX (where R is an organic group, and X is a halogen), demonstrating a metal-carbon bond. - Zeise's salt contains a transition metal (platinum) bonded to an ethylene group, forming a metal-carbon bond.

Step 3: Identify the Non-Organometallic Compound

Compare each option's characteristics against the definition in Step 1. Cisplatin lacks a direct metal-carbon bond and is thus not an organometallic compound. Meanwhile, the other compounds include metal-carbon bonds characteristic of organometallic compounds.

Key Concepts

Metal-Carbon Bond

Metal-carbon bonds form the backbone of organometallic chemistry. These bonds occur when a carbon atom from an organic group connects with a metal atom. This connection is crucial as it significantly alters the chemical reactivity and properties of the organic molecules involved.

• For example, in Grignard's reagent, the carbon atom is bonded to magnesium, signifying a typical metal-carbon interaction.
• The strength of a metal-carbon bond can vary considerably depending on the nature of the metal and the organic group.

Understanding these bonds is essential for predicting how organometallic compounds will behave in chemical reactions. It also helps chemists design new compounds with specific desired properties.

Transition Metals

Transition metals play a pivotal role in the formation of organometallic compounds. Many of these metals, such as iron, cobalt, and platinum, are capable of forming stable metal-carbon bonds due to their unique electronic structures.

• These metals have partially filled d-orbitals which can overlap with the orbitals of carbon atoms.
• This overlapping allows for the formation of coordination complexes, especially stable ones.

Transition metals are not only prominent in industrial applications but also in academic research due to their versatility in forming various compounds with intriguing properties.

Grignard's Reagent

Grignard's reagent is a powerful tool in organic synthesis. Typically formulated as RMgX (where R is an alkyl or aryl group, and X is a halogen), it showcases the metal-carbon bond by featuring magnesium directly bonded to a carbon atom from an organic compound.

• Because of this bond, Grignard reagents are highly reactive and can be used to form carbon-carbon bonds, playing a crucial role in the construction of complex molecular structures.
• They are particularly useful for introducing new carbon frameworks into a molecule.

The versatility of Grignard's reagent has made it a staple in the toolkit of organic chemists, allowing for the synthesis of a broad range of chemical compounds.

Coordination Complex

Coordination complexes are structures formed when central metal atoms bond with surrounding ligands. Although not organsometallic, as these do not always include a metal-carbon bond, they are a crucial area of study in inorganic chemistry.

• Cisplatin, for example, is a coordination complex of platinum with ligands like ammonia and chloride.
• These complexes do not qualify as organometallic compounds unless a direct metal-carbon bond is present.

Understanding coordination complexes is essential for recognizing the boundaries of organometallic chemistry and appreciating the diversity of compounds within chemistry as a whole.