Question

The IUPAC name of \[\left[ {Cr{{\left( {{H_2}O} \right)}_4}C{l_2}} \right]Cl\] is:
A. Tetrahydro dichlorido chromium (II) chloride
B. Tetrahydro dichlorido chromium (I) chloride
C. Tetrahydro dichlorido chromium (III) chloride
D. None of these

Answer 1

Hint: For coordination compounds, we must apply the IUPAC naming convention. The oxidation state of the metal ion is determined by the charges of the ligands.

Complete Step by Step Solution:
The given complex is \[\left[ {Cr{{\left( {{H_2}O} \right)}_4}C{l_2}} \right]Cl\] .
The ligands are named first, the central metal atom is named last, and the ligand is called in alphabetical sequence, according to the IUPAC naming system. Ending O is used to name negative ligands. The suffix –ium is used for positively charged ligands. With a few exceptions, neutral ligands are given their typical names. For multiple monodentate ligands, use the Greek prefix di, tri; for multiple polydentate ligands, use the prefix bis, tris. The oxidation state of the metal ion is indicated by the Roman numeral in parenthesis. If the complex is an anion, use the suffix-ate for the center metal atom.
Here, in this complex, the central metal is \[Cr\] and ligands are \[{H_2}O\] and \[Cl\].
The hydro term is used for \[{H_2}O\] . There are four \[{H_2}O\] ligands and the tetra- suffix is being used for four. Therefore, it can be written as tetrahydro.
Chlorido term is used for \[Cl\]. There are two \[Cl\] ligands and the di- suffix is being used for two. Therefore, it can be written as dichlorido.
One \[Cl\] outside the square bracket indicates chloride ion. It has \[ - 1\] charge on it. This is written as chloride.
Chromium has \[ + 3\] oxidation state. Therefore, the name of the complex is tetrahydro dichlorido chromium (III) chloride.
Therefore, the correct answer is option C tetrahydro dichlorido chromium (III) chloride.

Note: The charges on the ligands are used to calculate the oxidation state of the metal ion. The prefix di, tri, and so on have no bearing on the alphabetical order of ligands.