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Ch.23 - Transition Metals and Coordination Chemistry
All textbooksBrown 14th EditionCh.23 - Transition Metals and Coordination ChemistryProblem 7
Chapter 23, Problem 7

Complete the exercises below. a. A compound with formula RuCl₃ • 5H₂O is dissolved in water, forming a solution that is approximately the same color as the solid. Immediately after forming the solution, the addition of excess AgNO₃ (aq) forms 2 mol of solid AgCl per mole of complex. Write the formula for the compound, showing which ligands are likely to be present in the coordination sphere.

Verified step by step guidance
1
Step 1: Understand the problem by identifying the components of the compound. The compound given is RuCl₃ • 5H₂O, which consists of ruthenium chloride and water molecules.
Step 2: Recognize that the compound is a coordination complex. In coordination chemistry, the coordination sphere includes the central metal atom and its attached ligands. Here, Ru is the central metal.
Step 3: Analyze the reaction with AgNO₃. The formation of 2 mol of AgCl per mole of complex suggests that 2 chloride ions are free and not part of the coordination sphere, as they react with Ag⁺ to form AgCl.
Step 4: Determine the coordination sphere. Since 2 Cl⁻ ions are outside the coordination sphere, 1 Cl⁻ ion is likely coordinated to Ru. The 5 water molecules (5H₂O) are potential ligands, likely coordinating with Ru as well.
Step 5: Write the formula for the coordination complex. Based on the analysis, the coordination sphere likely includes Ru, 1 Cl⁻, and 5 H₂O, resulting in the formula [RuCl(H₂O)₅]Cl₂, where the brackets indicate the coordination sphere.

Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Coordination Compounds

Coordination compounds consist of a central metal atom or ion bonded to surrounding molecules or ions called ligands. In this case, RuCl₃ • 5H₂O indicates that ruthenium is the central metal, with chloride ions and water molecules acting as ligands. Understanding the nature of these ligands is crucial for predicting the compound's behavior in solution.
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Coordination Compound Naming

Ligands and Their Types

Ligands can be classified as monodentate, bidentate, or polydentate based on the number of donor atoms they use to bind to the central metal. In RuCl₃ • 5H₂O, water acts as a monodentate ligand, while chloride ions can also be considered monodentate. Recognizing the types of ligands helps in understanding the geometry and stability of the coordination complex.
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Precipitation Reactions

A precipitation reaction occurs when two soluble reactants form an insoluble product, or precipitate. In this scenario, the addition of AgNO₃ leads to the formation of AgCl, which precipitates out of the solution. This concept is essential for understanding how the complex interacts with other ions in solution and the stoichiometry involved in the reaction.
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Related Practice
Textbook Question

Four-coordinate metals can have either a tetrahedral or a square-planar geometry; both possibilities are shown here for [PtCl2(NH3)2].

a. What is the name of this molecule?

b. Would the tetrahedral molecule have a geometric isomer?

c. Would the tetrahedral molecule be diamagnetic or paramagnetic?

d. Would the square-planar molecule have a geometric isomer?

Textbook Question

Which of these crystal-field splitting diagrams represents:

a. a weak-field octahedral complex of Fe³⁺ ,

b. a strong-field octahedral complex of Fe³⁺ 

c. a tetrahedral complex of Fe³⁺

d. a tetrahedral complex of Ni²⁺ (The diagrams do not indicate the relative magnitudes of ∆. ) [Find more in Section 23.6.]

Textbook Question

In the linear crystal-field shown here, the negative charges are on the z-axis. Using Figure 23.28 as a guide, predict which of the following choices most accurately describes the splitting of the d orbitals in a linear crystal-field? [Find more in Section 23.6.]