Textbook Question
Draw the structure of the following complexes. What are the oxidation state, coordination number, and coordination geometry of the metal in each?
(a) Na[Au(CN)2]
Ch.21 - Transition Elements and Coordination Chemistry
Chapter 21, Problem 73b
Draw the structure of the following complexes. What are the oxidation state, coordination number, and coordination geometry of the metal in each?
(b) [Co(H2O)5Cl]SO4]
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Identify the central metal ion in the complex. In this case, it is cobalt (Co).
Determine the ligands attached to the central metal ion. Here, the ligands are five water molecules (H2O) and one chloride ion (Cl^-).
Calculate the oxidation state of the metal. Assume the sulfate ion (SO4^2-) is a counter ion and does not affect the oxidation state of cobalt. The complex is neutral, so the sum of the charges of the ligands and the metal must equal zero.
Determine the coordination number, which is the number of ligand donor atoms bonded to the central metal ion. In this complex, there are six ligands (five H2O and one Cl^-), so the coordination number is 6.
Identify the coordination geometry. With a coordination number of 6, the most common geometry is octahedral.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Oxidation State
The oxidation state of an element in a compound indicates the degree of oxidation or reduction of that element. It is determined by the number of electrons lost or gained compared to the neutral atom. In coordination complexes, the oxidation state of the metal can be calculated by considering the charges of the ligands and the overall charge of the complex.
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Oxidation Numbers
Coordination Number
The coordination number refers to the number of ligand atoms that are directly bonded to the central metal atom in a coordination complex. It is a crucial factor in determining the geometry and stability of the complex. For example, in the complex [Co(H2O)5Cl]SO4, the coordination number is 6, as there are five water molecules and one chloride ion coordinating to cobalt.
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Coordination Geometry
Coordination geometry describes the spatial arrangement of the ligands around the central metal atom in a coordination complex. Common geometries include octahedral, tetrahedral, and square planar, which are determined by the coordination number and the steric and electronic properties of the ligands. In the case of [Co(H2O)5Cl]SO4, the geometry is octahedral due to the coordination number of 6.
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Related Practice
Textbook Question
Draw the structure of the following complexes. What are the oxidation state, coordination number, and coordination geometry of the metal in each?
(b) [Cr(NH3)2(C2O4)2]NO2
Textbook Question
Draw the structure of the following complexes. What are the oxidation state, coordination number, and coordination geometry of the metal in each?
(a) Pt(en)2
Textbook Question
(a) Identify the Lewis acid and the Lewis base in the reaction of ethylenediamine (H2NCH2CH2NH2) with Ni2+ to form [Ni(en)3]2+.
(b) Identify the ligands and donor atoms.
(c) Give the coordination number and geometry of the metal in the complex.