Question

Write the formula of the following complex.
Pentamine carbonato chromium (III) chloride

Answer 1

Hint: If the complex has a positive charge the word ‘ion’ is written at the ending of its name. if the complex has a negative charge the name is written ending with the suffix ‘-ate’. As none of these is written the complex is a neutral complex.

Complete step by step answer:
The rules for writing the formula for coordination complex from the IUPAC name of coordination complex are as follows:
1The formula for the complex is written in the square parenthesis ‘[ ]’. The ligands in the second coordination sphere are written outside the parentheses.
2.The ligands are named first. The number of ligands are indicated by the suffix mono-, di-, tri-, tetra- penta-, and so on.
Thus, pentamine indicates that five amine ligands are present. The formula for amine ligand is $\text{N}{\text{H}}_{\text{3}}$.
And, carbonato indicates that one carbonate ligand is present. The formula for carbonate ligand is $\text{C}{\text{O}}_3$.
3.The name of the metal is written after the names of the ligands.
Thus, chromium indicates that the central metal atom is chromium. The formula for chromium is $\text{Cr}$.
4.The charge on the metal is indicated with the Roman numerals and written in the parenthesis after the name of the metal.
Thus, (III) indicates that the charge on the chromium metal atom is $+3$.
5.The ligand in the second coordination sphere is written after the name of the metal.
Thus, chloride indicates that one chloride ligand is outside the parentheses. The formula for chloride ion is $\text{Cl}$.
Thus, the formula for the complex Pentamine carbonato chromium (III) chloride is $\left[\text{Cr}{\left(\text{N}{\text{H}}_{\text{3}}\right)}_{\text{5}}\left(\text{C}{\text{O}}_{\text{3}}\right)\right]\text{Cl}$.

Note:
The amine $\left(\text{N}{\text{H}}_{\text{3}}\right)$ ligand is a neutral ligand and it does not have any charge. The carbonato $\left(\text{C}{\text{O}}_3\right)$ ligand is a negatively charged ligand and it has a charge of $-2$.