Chapter 20: Problem 49
Give the coordination number of the central metal ion in (a) \(\left[\mathrm{Pt}(\mathrm{en})_{2}\right]^{2+}\) (b) \(\left[\mathrm{Cu}\left(\mathrm{C}_{2} \mathrm{O}_{4}\right)_{2}\right]^{2-}\).
Short Answer
Expert verified
(a) 4
(b) 4
Step by step solution
01
- Understand Coordination Number
The coordination number of a central metal ion in a complex is determined by counting the number of ligand atoms that are bonded directly to the metal ion.
02
- Recognize Ligands in [Pt(en)2]2+
The complex \[\left[\mathrm{Pt}(\mathrm{en})_{2}\right]^{2+}\]contains ethylenediamine (en) ligands. Each ethylenediamine ligand is a bidentate ligand, meaning it forms two bonds with the central metal ion, Pt.
03
- Calculate Coordination Number for [Pt(en)2]2+
There are two ethylenediamine ligands present. Since each ligand forms 2 bonds, the coordination number is: \[2 \text{ ligands} \times 2 \text{ bonds per ligand} = 4\]. Thus, the coordination number of \(\left[\mathrm{Pt}(\mathrm{en})_{2}\right]^{2+}\) is 4.
04
- Recognize Ligands in [Cu(C2O4)2]2-
The complex \[\left[\mathrm{Cu}\left(\mathrm{C}_{2}\mathrm{O}_{4}\right)_{2}\right]^{2-}\]contains oxalate (\(\mathrm{C}_{2}\mathrm{O}_{4}^{2-}\)) ligands. Each oxalate ligand is also a bidentate ligand, forming two bonds with the central metal ion, Cu.
05
- Calculate Coordination Number for [Cu(C2O4)2]2-
There are two oxalate ligands present. Since each ligand forms 2 bonds, the coordination number is: \[2 \text{ ligands} \times 2 \text{ bonds per ligand} = 4\]. Thus, the coordination number of \[\left[\mathrm{Cu}\left(\mathrm{C}_{2}\mathrm{O}_{4}\right)_{2}\right]^{2-}\]is 4.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Central Metal Ion
In the realm of coordination chemistry, the "central metal ion" holds a pivotal role in defining the structure and properties of a coordination complex. A coordination complex consists of a central metal ion surrounded by molecules or ions known as ligands.
These ligands bind to the metal ion through coordinate covalent bonds, where the ligand donates a pair of electrons to the metal for bonding.
These ligands bind to the metal ion through coordinate covalent bonds, where the ligand donates a pair of electrons to the metal for bonding.
- The central metal ion is often a transition metal, due to its ability to adopt various oxidation states and coordinate with different ligands.
- This central ion acts as an electron pair acceptor, playing a crucial role as a Lewis acid.
- The coordination number of a central metal ion signifies the total number of ligand points of attachment that are connected directly to it.
Bidentate Ligand
A bidentate ligand is a type of ligand that has two "teeth" or atoms allowing it to bind to the central metal ion at two distinct points. This leads to the formation of a chelate ring, providing extra stability to the complex structure.
The prefix 'bi-' implies that there are two donor atoms available for bonding.
The prefix 'bi-' implies that there are two donor atoms available for bonding.
- Bidentate ligands possess two donor atoms, such as nitrogen or oxygen, capable of forming coordinate bonds with the same metal ion.
- The creation of chelate rings is significant as it increases the thermodynamic stability of the complexes compared to those with monodentate ligands.
- The presence of bidentate ligands can alter the electronic properties and geometry of the metal complexes, affecting color, magnetic properties, and reactivity.
Ethylenediamine Ligand
Ethylenediamine, often abbreviated as "en," is a classic example of a bidentate ligand. It is a simple organic molecule composed of two amine groups connected by an ethylene (-CH2CH2-) bridge.
This configuration allows ethylenediamine to effectively coordinate with a central metal ion at two points.
This configuration allows ethylenediamine to effectively coordinate with a central metal ion at two points.
- Ethylenediamine has two nitrogen atoms, each possessing a lone electron pair that can coordinate with a metal ion.
- In coordination complexes like \([\mathrm{Pt}(\mathrm{en})_{2}]^{2+}\), the ethylenediamine ligand binds to the metal at both nitrogen atoms, forming stable, five-membered rings.
- This particular ligand is frequently used in coordination chemistry due to its ability to form stable chelate complexes with a variety of metal ions.