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Ch.23 - Transition Metals and Coordination Chemistry
All textbooksBrown 14th EditionCh.23 - Transition Metals and Coordination ChemistryProblem 2
Chapter 23, Problem 2

Draw the structure for Pt (en) Cl₂ and use it to answer the following questions: a. What is the coordination number for platinum in this complex? b. What is the coordination geometry? c. What is the oxidation state of the platinum? d. How many unpaired electrons are there? [Find more in Sections 23.2 and 23.6.]

Verified step by step guidance
1
Step 1: Identify the components of the complex. The complex is Pt(en)Cl₂, where 'en' stands for ethylenediamine, a bidentate ligand, and Cl represents chloride ions.
Step 2: Determine the coordination number. The coordination number is the number of ligand atoms directly bonded to the central metal. Ethylenediamine (en) is a bidentate ligand, meaning it forms two bonds with the metal. With two chloride ions, the total coordination number is 4.
Step 3: Determine the coordination geometry. For a coordination number of 4, the possible geometries are square planar or tetrahedral. Platinum(II) complexes, like Pt(en)Cl₂, typically adopt a square planar geometry.
Step 4: Calculate the oxidation state of platinum. Assign oxidation states to the ligands: ethylenediamine is neutral, and each chloride ion has a -1 charge. Let the oxidation state of Pt be x. The equation is x + 0 + 2(-1) = 0, solving for x gives the oxidation state of Pt.
Step 5: Determine the number of unpaired electrons. Platinum in a square planar complex with an oxidation state of +2 typically has a d⁸ electron configuration. In a square planar field, the d orbitals split such that there are no unpaired electrons.

Key Concepts

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

Coordination Number

The coordination number refers to the number of ligand atoms that are directly bonded to a central metal atom in a coordination complex. In the case of Pt(en)Cl₂, 'en' represents ethylenediamine, a bidentate ligand that binds through two donor atoms, while Cl is a monodentate ligand. Thus, the coordination number is the sum of the number of bonds formed by all ligands.
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Coordination Numbers

Coordination Geometry

Coordination geometry describes the spatial arrangement of the ligands around the central metal atom. For complexes with a coordination number of 4, such as Pt(en)Cl₂, the common geometries are tetrahedral and square planar. The specific geometry can be determined by the nature of the ligands and the electronic configuration of the metal.
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Oxidation State

The oxidation state of a metal in a complex indicates the charge of the metal ion after accounting for the charges of the ligands. In Pt(en)Cl₂, ethylenediamine is a neutral ligand, while each chloride ion has a -1 charge. By balancing the overall charge of the complex, one can deduce the oxidation state of platinum, which is crucial for understanding its reactivity and bonding.
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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.]