Question

IUPAC name of the compound \([\text{Co}(\text{NH}_3)_5\text{ONO}]\text{Cl}_2\) is

Hint:

Pay special attention to ambidentate ligands. If it is written as \(\text{NO}_2\), it's "nitrito-N". If written as \(\text{ONO}\), it's "nitrito-O". Also, remember to spell "ammine" with double 'm'.

Answer 1

Step 1: Understanding the Concept:
Naming coordination compounds follows strict IUPAC nomenclature rules. The cation is named before the anion. Within the complex ion, ligands are named in alphabetical order, followed by the central metal atom and its oxidation state in Roman numerals.
Step 2: Key Formula or Approach:
The approach involves identifying the ligands, determining their alphabetical order, calculating the oxidation state of the central metal, and identifying the linkage of ambidentate ligands. Let the oxidation state of the metal be \(x\) and use the formula: \(\sum (\text{charges of all components}) = \text{net charge of complex}\).
Step 3: Detailed Explanation:
Let's break down the complex \([\text{Co}(\text{NH}_3)_5\text{ONO}]\text{Cl}_2\):
1. Identify the parts: The complex cation is \([\text{Co}(\text{NH}_3)_5\text{ONO}]^{2+}\) and the counter anions are two \(\text{Cl}^-\) (chloride).
2. Name the ligands:
- There are five \(\text{NH}_3\) ligands. \(\text{NH}_3\) is named "ammine". Since there are five, we use the prefix "penta", making it "pentaammine".
- There is one \(\text{ONO}^-\) ligand. This is an ambidentate ligand derived from nitrite. Because it is written as ONO, it is coordinating through the oxygen atom. Therefore, it is named "nitrito-O".
3. Alphabetize ligands: "ammine" comes before "nitrito-O".
4. Calculate Oxidation State of Cobalt (Co):
Let \(x\) be the oxidation state of Co.
Charge of \(\text{NH}_3 = 0\)
Charge of \(\text{ONO}^- = -1\)
Charge of the complex sphere \([\text{Co}(\text{NH}_3)_5\text{ONO}]^{2+}\) must be \(+2\) to balance the two \(\text{Cl}^-\) ions.
\[ x + 5(0) + (-1) = +2 \]
\[ x - 1 = 2 \]
\[ x = +3 \]
So, the oxidation state is (III).
5. Assemble the name:
Combine the ligand names, metal name, and oxidation state: pentaamminenitrito-O-cobalt(III).
Add the counter ion at the end: chloride.
Step 4: Final Answer:
The full IUPAC name is pentaamminenitrito-O-cobalt(III) chloride.