Naming Coordination Compounds : Videos & Practice Problems

Naming coordination compounds involves systematic rules, particularly for ligands, which can be anions or neutral molecules. Anionic ligands like bromide (bromo) and hydroxide (hydroxo) follow a specific naming convention, while neutral ligands such as water (aqua) and ammonia (amine) retain their names. Transition metals have standard names, but some, like iron (ferrate) and copper (cuprate), use Latin-based names. When naming coordination complexes, the cation precedes the anion, distinguishing between complex ions and counter ions, essential for accurate nomenclature.

Ligand Naming

Naming coordination compounds follows a systematic approach established by the International Union of Pure and Applied Chemistry (IUPAC). A key aspect of this naming convention involves identifying ligands, which can be classified as either anions (negatively charged) or neutral molecules. In this context, we will focus on these two categories of ligands, excluding cationic ligands for simplicity.

For anionic ligands, the naming convention typically involves modifying the name of the ion. For instance, the bromide ion (Br^-) is referred to as bromo, while the oxide ion (O₂^-) is called oxo. Other examples include:

• Hydroxide (OH^-) becomes hydroxo.
• Cyanide (CN^-) is termed cyano.
• Azide (N₃^-) is known as azido.
• Nitrate (NO₃^-) is referred to as nitro, while nitrite (NO₂^-) is also called nitro.
• Oxalate (C₂O₄^2-) is named oxalato, and carbonate (CO₃^2-) is termed carbonato.

On the other hand, neutral ligands retain their original names, and their chemical formulas are straightforward. For example:

• Aqua corresponds to water (H₂O).
• Amine refers to ammonia (NH₃).
• Carbonyl is represented by carbon monoxide (CO).
• Nitroso corresponds to nitric oxide (NO).
• Ethylenediamine, often abbreviated as en, is a bidentate ligand that includes a numerical prefix indicating its structure.

Understanding these naming conventions for ligands is essential for accurately describing coordination compounds and their structures.

Naming Coordination Compounds Example

When naming ligands and complex ions, it is essential to follow a systematic approach. First, identify the ligands attached to the central metal ion, in this case, silver. The ligands can be classified as either anionic (negatively charged) or neutral.

For anionic ligands, the name is modified by changing the ending to "o." In this example, the chloride ion (Cl^-) is the anionic ligand, which is named "chloro." For neutral ligands, such as ethylenediamine (often abbreviated as "en"), the name remains unchanged.

When multiple identical ligands are present, prefixes are used to indicate their quantity: "di" for two, "tri" for three, and "tetra" for four. If a ligand already contains a numerical prefix, such as "di" in ethylenediamine, the ligand name is placed in parentheses, and the appropriate prefix is modified to "bis" for two, "tris" for three, and "tetrakis" for four.

In this specific case, there are two chloride ions, which would be named "dichloro." Since there are also two ethylenediamine ligands, they would be named "bis(ethylenediamine)." Therefore, the complete name of the complex ion would be "dichloro bis(ethylenediamine) silver." This systematic naming ensures clarity and consistency in the identification of complex ions and their ligands.

Complex Ion Naming

When naming complex ions, it is essential to recognize the role of transition metals and their corresponding names. Transition metals often have standard names, but some are derived from their Latin names, which can lead to variations in nomenclature. For instance, chromium, cobalt, manganese, and molybdenum typically retain their standard names, while others like iron, copper, silver, tin, gold, and lead adopt Latin-based names.

For example, iron, represented by the symbol Fe, is referred to as ferrate. Copper, with the symbol Cu, is named cuprate. Silver, denoted as Ag, takes the name argentate. Tin, represented by Sn, is called stannate. Gold, with the symbol Au, is referred to as aurate, and lead, denoted as Pb, is named plumbate.

These naming conventions are crucial for accurately identifying complex ions in coordination chemistry. Understanding the distinction between standard and Latin-based names allows for clearer communication and comprehension of chemical compounds. The systematic approach to naming ensures that each complex ion is recognized by its appropriate nomenclature, facilitating further study and application in the field of chemistry.

Naming Coordination Compounds Example

To name a complex ion, follow a systematic approach that involves identifying and ordering the ligands, naming the transition metal, and applying specific rules based on the charge of the complex. Start by naming the ligands in alphabetical order, using prefixes to indicate the number of each type. For example, if there are two chloride ions, you would use the prefix "dichloro," and for two ethylenediamine ligands, you would use "bis" followed by "ethylenediamine." This results in the ligand portion being "dichlorobisethylenediamine."

Next, name the transition metal. If the complex ion is an anion, as in this case, modify the metal's name by changing its ending to "ate." For silver, which has a Latin name, this becomes "argentate." Additionally, include the oxidation state of the metal in Roman numerals in parentheses immediately following the metal name. To determine the oxidation state, set up an equation based on the overall charge of the complex ion. In this example, the silver ion (x) plus the contributions from the ligands must equal the overall charge of -1. Given that each chloride ion contributes -1 and the ethylenediamines are neutral, the equation can be set up as follows:

$$x + 0 + 2(-1) = -1$$

Solving this gives:

$$x - 2 = -1 \implies x = +1$$

Thus, the oxidation state of silver is +1. Finally, combine all parts to form the complete name of the complex ion: "dichlorobisethylenediamine argentate(I)." Remember to remove all spaces to create a single string of letters, resulting in:

dichlorobisethylenediamineargentate(I).

Provide name of complex ion [Fe(CN)₅NO]^3–

• A. pentacyanidenitrosylferrate(II)
• B. pentacyanidenitroferrate(III)
• C. pentacyanonitrosylferrate(II)
• D. pentacyanonitroferrate(III)

Answer: (C)

Coordination Compound Naming

In the study of coordination complexes, understanding the naming conventions is crucial. Similar to naming ionic compounds, the name of the cation, which carries a positive charge, is placed before the anion, which carries a negative charge. The cation can either be a counter ion or a complex ion, making it essential to identify each component accurately.

For example, consider a coordination complex where potassium is connected to a complex ion represented within brackets. In this case, potassium acts as the counter ion, while the contents of the brackets denote the complex ion. Conversely, if the complex ion appears first in the name, followed by a counter ion such as chloride, the naming order remains consistent, with the complex ion leading.

Recognizing the distinction between the counter ion and the complex ion is vital for proper nomenclature. Additionally, identifying which component is the cation and which is the anion is essential for accurately naming coordination complexes. This systematic approach ensures clarity and precision in chemical communication.

Naming Coordination Compounds Example

To systematically name a coordination complex, follow these steps carefully. First, identify and name the ligands in alphabetical order. For negatively charged ligands, the ending is changed to "oxo," while neutral ligands retain their original names. Use numerical prefixes such as di, tri, and tetra for most ligands, but for ligands like ethylenediamine, which already include a prefix, use "bis," "tris," or "petrachis" instead.

Next, name the transition metal after the ligands, ensuring there are no spaces between the names. If the complex ion is a cation, the metal name remains unchanged. If it is an anion, the ending is modified to "ate." Additionally, some transition metals have Latin-based names, and a Roman numeral is added to indicate the charge of the metal. The overall charge of the complex ion is not included in the name but is essential for determining the metal's charge.

Finally, consider the counterion. If it is a cation, its name remains unchanged; if it is an anion, the ending changes to "ide." Polyatomic ions retain their names. When writing the full name of the coordination complex, the cation is named first, followed by the anion, with a space between the two.

For example, consider a complex with chromium, five water molecules, and one bromide ligand, resulting in an overall charge of +2. The ligands are named as follows: water is "aqua," and bromine is "bromo." Since there are five water molecules, it is named "pentaqua." The complex ion is thus "pentaquabromochromium." To determine the charge of chromium, set up the equation based on the charges: let x be the charge of chromium. The equation becomes:

$$x + 5(0) + 1(-1) = +2$$

Solving this gives:

$$x - 1 = 2 \implies x = +3$$

Thus, the chromium ion is "chromium(III)." The bromide counterion is named "bromide." Therefore, the complete name of the coordination complex is "pentaquabromochromium(III) bromide."

Provide a systematic name for K₂[Mo(O)Cl₄].

• A. Potassium tetrachlorocarbonylmolybdate(VI)
• B. Dipotassium tetrachlorocarbonylmolybdate(IV)
• C. Potassium tetrachloroxomolybdate(IV)
• D. Dipotassium tetrachloroxomolybdate(VI)

Answer: (C)

Provide name for the following coordination compound: [Ag(H₂O)₂]NO₃.

• A. Diaquasilver(I) nitrate
• B. Dihydroxidesilver(I) nitrate
• C. Diaquasilver(II) nitrosyl
• D. Dihydroxidesilver(II) nitrosyl

Answer: (A)

What is the systematic name of [Co(en)₂(NH₃)CN]Cl₂.

• A. Amminocyanodiethylenediaminecobalt(II) chloride
• B. Amminecyanobisethylenediaminecobalt(II) chloride
• C. Amminocyanodi(ethylenediamine)cobalt(III) chloride
• D. Amminecyanobis(ethylenediamine)cobalt(III) chloride

Answer: (D)

Here’s what students ask on this topic:

When naming coordination compounds, are ligands always listed?

Yes, when naming coordination compounds, ligands are always listed as part of the compound's name. The ligands are named before the metal ion in the chemical name. If there are multiple ligands, they are listed alphabetically regardless of charge or the number of each type of ligand present. Neutral ligands are usually given their common names, with some exceptions (e.g. water is called 'aqua'). Anionic ligands typically end in '-o' (e.g. chloride becomes 'chlorido'). Prefixes like di-, tri-, tetra-, etc., are used to indicate the number of each type of ligand if there is more than one. These prefixes are not considered when determining the alphabetical order of ligands. After naming the ligands, the metal is named, and its oxidation state is indicated in Roman numerals in parentheses. If the compound is an anionic complex, the name of the metal ends with the suffix '-ate'.

How to name coordination compounds?

Naming coordination compounds involves a specific set of rules to ensure that the chemical composition and structure of the compound are clearly communicated. Here's a simplified summary of the process:

1. Name the ligands first: Ligands are the ions or molecules attached to the central metal atom or ion in the coordination compound. Name them in alphabetical order, regardless of charge. Use prefixes like 'di-', 'tri-', 'tetra-', etc., to indicate the number of each type of ligand. Anionic ligands typically end in '-o' (e.g. chloride becomes chlorido), neutral ligands are often named as the molecule (e.g. water becomes aqua), except for a few special cases like ammonia, which is named as ammine.
2. Name the central metal: After the ligands, the name of the central metal atom or ion is given. If the complex is an anion, the metal name ends in '-ate' (e.g. iron becomes ferrate). For transition metals, the oxidation state of the metal is indicated in Roman numerals in parentheses immediately following the metal name.
3. Add prefixes for the entire complex: If the complex is a cation or a neutral molecule, no further changes are needed after naming the metal with its oxidation state. However, if the complex is an anion, the name of the