Question

How are the names of anionic ligands changed when they are part of the name of a coordination complex?

Short answer

Anionic ligands change their names by replacing the ending of the anion with 'o' when part of a coordination complex's name, (e.g., 'chloride' becomes 'chlorido'), except for a few common anions that have specific names.

Step-by-step solution

Understanding the Nomenclature for Anionic Ligands

When anionic ligands are part of a coordination complex, the names of the ligands are typically changed by replacing the ending of the anion with 'o'. For example, chloride becomes chlorido, sulfate becomes sulfato, and nitrate becomes nitrato. This rule applies to simple anionic ligands as well as polyatomic anionic ligands.

Applying the Rule to Multiple Examples

Let’s apply the rule to several examples. If the ligand is the anion 'bromide' (Br-), the name used in the coordination complex becomes 'bromido'. If 'cyanide' (CN-) is the ligand, it is named 'cyanido' in the complex. Similarly, 'hydroxide' (OH-) becomes 'hydroxido' within the complex name.

Recognizing Exceptions

There are some common exceptions to this rule, such as water which is known as 'aqua', ammonia as 'ammine', carbon monoxide as 'carbonyl', and nitric oxide as 'nitrosyl'. It's important to learn these exceptions as they are frequently used ligands in coordination chemistry.

Key concepts

Anionic Ligands Naming

When delving into the world of coordination complex nomenclature, understanding the naming of anionic ligands is vital. These negatively charged ligands, when part of a coordination complex, undergo a notable change: their endings are modified to end with 'o'. This transition eases the pronunciation and distinguishes the ligand within the complex.

For instance, 'chloride' transforms into 'chlorido', and 'oxide' becomes 'oxido'. It's such a straightforward alteration that, with a little practice, it becomes almost second nature to apply this rule. Remember, the 'ide' of the anion gets replaced by 'o', which is a helpful mnemonic to keep in mind.

Nomenclature Rules for Coordination Chemistry

The nomenclature rules in coordination chemistry serve as a universal language for scientists around the globe. Once you comprehend the basics, these rules lead to clear and unambiguous names for coordination compounds. Alongside anionic ligand naming, several other principles come into play. For instance, the name of the central metal is followed by oxidation state in Roman numerals set in parentheses. Ligands are listed before the metal, with neutral ligands typically retaining their molecular names.

However, with anionic ligands, as mentioned before, the 'ide' ending is altered to 'o'. With these ground rules as your foundation, diving deeper into complex naming becomes far more manageable, and you'll begin to notice patterns that simplify the learning process.

Polyatomic Anionic Ligand Names

Polyatomic anionic ligands are a captivating topic because they often carry more than just one atom and bring an extra layer of complexity to coordination chemistry. Similar to their monoatomic counterparts, the naming of these ligands involves changing their typical anion endings to 'o'.

For example, 'sulfate' (SO₄^2-) becomes 'sulfato', and 'carbonate' (CO₃^2-) is renamed 'carbonato'. This standardized practice allows chemists to quickly identify the presence of these ligands when reviewing complex names. As an exercise, try to rename 'phosphate' (PO₄^3-) within a coordination compound as a test of your understanding.

Naming Exceptions in Coordination Complexes

Finally, it's crucial to be aware of the exceptions in coordination complex nomenclature. Common ligands like water and ammonia have their distinct naming conventions, such as 'aqua' and 'ammine' respectively, instead of following the previously mentioned 'o' ending modification.

These exceptions are a testament to the historical development of chemistry where traditional names have been retained due to widespread usage. 'Carbon monoxide' and 'nitric oxide', are referred to as 'carbonyl' and 'nitrosyl' when serving as ligands. These special names must be memorized, as they do not follow the standard pattern but are frequently encountered in coordination chemistry.