Problem 37 - Chemistry The Central Science In Si Units

Question

Write the names of the following compounds, using the standard nomenclature rules for coordination complexes: (a) \(\left[\mathrm{Ag}\left(\mathrm{NH}_{3}\right)_{2}\right] \mathrm{NO}_{3}\) (b) \(\mathrm{Hg}\left[\mathrm{Co}(\mathrm{SCN})_{4}\right]\) (c) \(\left[\mathrm{Ru}\left(\mathrm{PPh}_{3}\right)_{3} \mathrm{Cl}_{3}\right]\) (d) \(\left[\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{5} \mathrm{CO}_{3}\right]_{2} \mathrm{SO}_{4}\)

Step-by-Step Solution

Answer

(a) Diammine silver(I) nitrate, (b) Mercury tetrathiocyanatocobaltate(II), (c) Trichloro(triphenylphosphine)ruthenium(III), (d) Pentamminecarbonatocobalt(III) sulfate.

Step 1: Naming the Cationic Complex

For compound (a) \(\left[\mathrm{Ag}\left(\mathrm{NH}_{3}\right)_{2}\right] \mathrm{NO}_{3}\), the complex \(\left[\mathrm{Ag}\left(\mathrm{NH}_{3}\right)_{2}\right]^+\) is a cation. The ligand \(\mathrm{NH}_3\) is named 'ammine'. The complex is named 'diammine'. Since \(\mathrm{Ag}^+\) (silver ion) is the central metal and not in an anion, we name it 'silver', leading to 'diammine silver' followed by 'nitrate' for \(\mathrm{NO}_3^-\). The full name is 'diammine silver(I) nitrate'.

Step 2: Naming the Anionic Complex

For compound (b) \(\mathrm{Hg}\left[\mathrm{Co}(\mathrm{SCN})_{4}\right]\), the complex \(\left[\mathrm{Co}(\mathrm{SCN})_{4}\right]^{2-}\) is an anion. The ligand \(\mathrm{SCN}^-\) is called 'thiocyanato'. The prefix 'tetra' indicates four ligands, thus 'tetrathiocyanato'. The metal \(\mathrm{Co}\) in an anionic complex is named 'cobaltate'. Mercury acts as the cation and has no charge indication in the name. The full name is 'mercury tetrathiocyanatocobaltate(II)'.

Step 3: Naming the Neutral Complex

For compound (c) \(\left[\mathrm{Ru}\left(\mathrm{PPh}_{3}\right)_{3}\mathrm{Cl}_{3}\right]\), the complex is neutral. The ligand \(\mathrm{PPh}_3\) is 'triphenylphosphine' and \(\mathrm{Cl}^-\) is 'chloro'. There are three of each, hence 'trichloro' and 'tris(triphenylphosphine)'. The metal \(\mathrm{Ru}\) is 'ruthenium'. The full name is 'trichloro(triphenylphosphine)ruthenium(III)'.

Step 4: Naming the Cationic Complex with Charged Ligands

For compound (d) \(\left[\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{5} \mathrm{CO}_{3}\right]_{2} \mathrm{SO}_{4}\), the complex \(\left[\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{5} \mathrm{CO}_{3}\right]^{2+}\) is a cation. The ligand \(\mathrm{NH}_3\) is 'ammine' and \(\mathrm{CO}_3^{2-}\) is 'carbonato'. The prefix 'penta' indicates five \(\mathrm{NH}_3\) ligands, forming 'pentammine'. \(\mathrm{Co}\) is 'cobalt' due to the complex's positive charge. The full name is 'pentamminecarbonatocobalt(III) sulfate'.

Key Concepts

Cationic Complex Naming

When naming a coordination complex that acts as a cation, there are specific rules that must be followed. First, identify the ligands attached to the central metal ion and name them. For neutral ligands, like ammonia, you would use the name 'ammine'. If there are multiple identical ligands, prefixes such as 'di-' for two or 'penta-' for five are used to indicate the quantity.
After naming the ligands, the central metal is named using its regular name, without any alteration. Importantly, include the oxidation state of the metal in Roman numerals after its name, enclosed in parentheses. The example we have involves a compound, a. \[\left[\mathrm{Ag}\left(\mathrm{NH}_{3}\right)_{2}\right] \mathrm{NO}_{3}\], the metal 'silver' is in the complex ion, so it's called 'diammine silver(I) nitrate'.
The 'nitrate' signals the presence of the anion \(\mathrm{NO}_3^-\), commonly associated with cationic complexes.

Anionic Complex Naming

For anionic coordination complexes, the naming rules slightly differ from their cationic counterparts. In these cases, the ligands are named similarly; however, the metal name integrates 'ate' at the end.
Identify the ligands using their respective names, and if there are multiples, use appropriate prefixes like 'tetra-'. Thiocyanato for instance might appear as 'tetrathiocyanato' if there are four ligands involved.
Crucially, the central metal's name changes. Instead of its usual name, add 'ate', such as 'cobaltate' for cobalt. Its oxidation state, in Roman numerals, stays intact. For instance, in compound b. \[\mathrm{Hg}\left[\mathrm{Co}(\mathrm{SCN})_{4}\right]\], the full name is 'mercury tetrathiocyanatocobaltate(II)', highlighting mercury as the non-complex part.

Neutral Complex Naming

Naming a neutral coordination complex involves identifying the ligands and their quantities just as previously mentioned.
For neutral complexes, you don't require additional names for the metal. This version of nomenclature keeps the central metal in its elemental state without any suffixes.
Identify the coordination number by counting ligands, and use the prefixes accordingly. Ligands themselves are named using standard nomenclature appropriate to their chemical type, like 'triphenylphosphine' or 'chloro'. For example, in compound c. \[\left[\mathrm{Ru}\left(\mathrm{PPh}_{3}\right)_3\mathrm{Cl}_{3}\right]\], with three ligands total of each type, you end up with 'trichloro' and 'tris(triphenylphosphine)' coupled with the metal name 'ruthenium'. This results in the name 'trichloro(tris(triphenylphosphine)ruthenium(III)', showing it as a neutral coordination complex.