Textbook Question
In octahedral complexes, the choice between high-spin and low-spin electron configurations arises only for d4 - d7 complexes. Explain.
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Ch.21 - Transition Elements and Coordination Chemistry
McMurry8th EditionChemistryISBN: 9781292336145
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Table of contents
- Ch.1 - Chemical Tools: Experimentation & Measurement143
- Ch.2 - Atoms, Molecules & Ions134
- Ch.3 - Mass Relationships in Chemical Reactions149
- Ch.4 - Reactions in Aqueous Solution157
- Ch.5 - Periodicity & Electronic Structure of Atoms92
- Ch.6 - Ionic Compounds: Periodic Trends and Bonding Theory73
- Ch.7 - Covalent Bonding and Electron-Dot Structures47
- Ch.8 - Covalent Compounds: Bonding Theories and Molecular Structure51
- Ch.9 - Thermochemistry: Chemical Energy104
- Ch.10 - Gases: Their Properties & Behavior138
- Ch.11 - Liquids & Phase Changes43
- Ch.12 - Solids and Solid-State Materials56
- Ch.13 - Solutions & Their Properties98
- Ch.14 - Chemical Kinetics79
- Ch.15 - Chemical Equilibrium107
- Ch.16 - Aqueous Equilibria: Acids & Bases94
- Ch.17 - Applications of Aqueous Equilibria125
- Ch.18 - Thermodynamics: Entropy, Free Energy & Equilibrium66
- Ch.19 - Electrochemistry130
- Ch.20 - Nuclear Chemistry73
- Ch.21 - Transition Elements and Coordination Chemistry122
- Ch.22 - The Main Group Elements155
- Ch.23 - Organic and Biological Chemistry43
Chapter 21, Problem 98
Consider the octahedral complex [Co(en)(dien)Cl]2+, where dien = H2NCH2CH2NHCH2CH2NH2, which can be abbreivated
(a) The dien (diethylenetriamine) ligand is a tridentate ligand. Explain what is meant by 'tridentate' and why dien can act as a tridentate ligand.
(b) Draw all possible stereoisomers of [Co(en)(dien)Cl]2+ (dien is a flexible ligand). Which stereoisomers are chiral, and which are achiral?
Verified step by step guidance1
**Step 1:** Understand the term 'tridentate'. A tridentate ligand is a ligand that can form three bonds to a central metal atom or ion. This is due to the presence of three donor atoms within the ligand that can each donate a pair of electrons to the metal center.
**Step 2:** Analyze the structure of dien (diethylenetriamine). Dien has three nitrogen atoms, each with a lone pair of electrons, which can coordinate to a metal center, making it a tridentate ligand.
**Step 3:** Consider the coordination environment in the complex [Co(en)(dien)Cl]^{2+}. The cobalt ion is in an octahedral coordination environment, which means it can form six bonds with ligands. Here, 'en' (ethylenediamine) is a bidentate ligand, 'dien' is tridentate, and there is one chloride ion.
**Step 4:** Draw the possible stereoisomers. In an octahedral complex with bidentate and tridentate ligands, different spatial arrangements can lead to stereoisomers. Consider the different ways the ligands can be arranged around the cobalt center.
**Step 5:** Determine chirality. A complex is chiral if it cannot be superimposed on its mirror image. Examine each stereoisomer to see if it has a plane of symmetry (achiral) or lacks one (chiral).
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Tridentate Ligands
A tridentate ligand is a type of chelating agent that can form three bonds to a central metal atom or ion. In the case of diethylenetriamine (dien), it has three nitrogen atoms that can coordinate with the metal center, allowing it to effectively 'wrap around' the metal and stabilize the complex. This multi-point attachment enhances the stability of the metal-ligand complex compared to monodentate ligands, which bind through only one atom.
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Ligands Example
Stereoisomerism
Stereoisomerism refers to the phenomenon where compounds have the same molecular formula and connectivity of atoms but differ in the spatial arrangement of those atoms. In octahedral complexes like [Co(en)(dien)Cl]2+, the arrangement of ligands around the central metal can lead to different stereoisomers, including geometric isomers (cis/trans) and optical isomers (enantiomers), which are crucial for understanding the properties and reactivity of the complex.
Chirality
Chirality is a property of a molecule that makes it non-superimposable on its mirror image, much like left and right hands. In coordination complexes, chirality arises when the arrangement of ligands creates an asymmetric environment around the metal center. Chiral stereoisomers can exhibit different optical activities, which is important in fields like pharmacology, where the activity of enantiomers can differ significantly.
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Related Practice
Textbook Question
Write the formula for each of the following compounds.
(c) Hexacarbonylmolybdenum(0)
(d) Diamminebis(ethylenediamine)chromium(III) chloride
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Textbook Question
The reaction of the octahedral complex Co(NH3)3(NO2)3 with HCl yields a complex [Co(NH3)3(H2O)Cl2]+ in which the two chloride ligands are trans to one another.
(a) Draw the two possible stereoisomers of the starting material [Co(NH3)3(NO2)3]. (All three NO2- ligands are bonded to Co through the N atom.)
(b) Assuming that the NH3 groups remain in place, which of the two starting isomers could give rise to the observed product?
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Textbook Question
Tris(2-aminoethyl)amine, abbreviated tren, is the tetradentate ligand N(CH2CH2NH2)3. Using to represent each of the three NCH2CH2NH2 segments of the ligand, sketch all possible isomers of the octahedral complex [Co(tren)BrCl]+.
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Textbook Question
Which of the following complexes are chiral?
(a) Pt(en)Cl2
(b) cis-[Co(NH3)4Br2]+
(c) cis-[Cr(en)2(H2O)2]3+
(d) [Cr(C2O4)3]3-