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What is the coordination number of the metal ion in the complex [Ni(NH3)4]?
What is the coordination number of the metal ion in the complex [Ni(NH3)4]?
What is the term used to describe the number of ligating groups in a ligand?
What is the term used to describe the number of ligating groups in a ligand?
What type of ligand can bind a metal ion through two different donor atoms?
What type of ligand can bind a metal ion through two different donor atoms?
What is the term used to describe a ligand that uses two or more donor atoms to bind a single metal ion?
What is the term used to describe a ligand that uses two or more donor atoms to bind a single metal ion?
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What is the coordination number of the metal ion in the complex [PtCl6]?
What is the coordination number of the metal ion in the complex [PtCl6]?
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Which of the following ions can coordinate through different donor atoms?
Which of the following ions can coordinate through different donor atoms?
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What is the advantage of chelate complexes over similar complexes containing unidentate ligands?
What is the advantage of chelate complexes over similar complexes containing unidentate ligands?
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What is the term used to describe a complex that contains a ligand that uses two or more donor atoms to bind a single metal ion?
What is the term used to describe a complex that contains a ligand that uses two or more donor atoms to bind a single metal ion?
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What is the coordination number of a metal ion?
What is the coordination number of a metal ion?
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What type of ligand can bind a metal ion through multiple donor atoms?
What type of ligand can bind a metal ion through multiple donor atoms?
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Study Notes
Coordination Compounds
- Coordination number of Fe and Co in [Fe(C2O4)3] and [Co(en)3] is 6 because C2O42– and en (ethane-1,2-diamine) are didentate ligands.
Coordination Sphere
- The central atom/ion and the ligands attached to it are enclosed in square brackets and collectively termed as the coordination sphere.
- The ionisable groups are written outside the bracket and are called counter ions.
- Example: in K4[Fe(CN)6], the coordination sphere is [Fe(CN)6]4– and the counter ion is K+.
Coordination Polyhedron
- The spatial arrangement of the ligand atoms which are directly attached to the central atom/ion defines a coordination polyhedron about the central atom.
- The most common coordination polyhedra are octahedral, square planar, and tetrahedral.
- Examples: [Co(NH3)6] is octahedral, [Ni(CO)4] is tetrahedral, and [PtCl4] is square planar.
Mononuclear Coordination Entities
- Mononuclear coordination entities contain a single central metal atom.
- Rules for writing formulas:
- The central atom is listed first.
- The ligands are then listed in alphabetical order.
- Polydentate ligands are also listed alphabetically.
- The formula for the entire coordination entity is enclosed in square brackets.
- Ligand abbreviations are enclosed in parentheses.
- No space between the ligands and the metal within a coordination sphere.
- When the formula of a charged coordination entity is to be written without the counter ion, the charge is indicated outside the square brackets as a right superscript.
Naming of Mononuclear Coordination Compounds
- The names of coordination compounds are derived by following the principles of additive nomenclature.
- The groups that surround the central atom must be identified in the name.
- A di- or polydentate ligand uses its two or more donor atoms simultaneously to bind a single metal ion, it is said to be a chelate ligand.
- The number of such ligating groups is called the denticity of the ligand.
- Chelate complexes tend to be more stable than similar complexes containing unidentate ligands.
- Ligand which has two different donor atoms and either of the two ligates in the complex is called ambidentate ligand.
Coordination Number
- The coordination number (CN) of a metal ion in a complex can be defined as the number of ligand donor atoms to which the metal is directly bonded.
- Examples: in the complex ions, [PtCl6] and [Ni(NH3)4], the coordination number of Pt and Ni are 6 and 4 respectively.
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Description
Understand the coordination number and coordination sphere in coordination compounds, including the role of ligands and counter ions.
