Problem 25 - Chemistry: The Central Science

Question

Write the names of the following compounds, using the standard nomenclature rules for coordination complexes: (a) \(\left[\mathrm{Rh}\left(\mathrm{NH}_{3}\right)_{4} \mathrm{Cl}_{2}\right] \mathrm{Cl}\) (b) \(\mathrm{K}_{2}\left[\mathrm{TiCl}_{6}\right]\) (c) \(\mathrm{MoOCl}_{4}\) (d) \(\left[\mathrm{Pt}\left(\mathrm{H}_{2} \mathrm{O}\right)_{4}\left(\mathrm{C}_{2} \mathrm{O}_{4}\right)\right] \mathrm{Br}_{2}\)

Step-by-Step Solution

Answer

tetraammine dichloridorhodium(III) chloride; potassium hexachloridotitanate(IV); tetrachlorido-oxido-molybdenum(VIII); tetraaqua oxalatoplatinum(II) bromide

Step 1: Identify central atom and ligands

The central atom is Rh(rhodium) and the ligands are four ammonia molecules (NH\(_3\)) and two chloride ions (Cl\(^-\)). Additionally, there is one chloride ion outside the square brackets acting as a counterion.

Step 2: Name the ligands

Ammonia as a ligand is named "ammine" and \(\mathrm{Cl}^-\) is named "chlorido".

Step 3: Combine the ligand and central atom names, along with appropriate oxidation state

The compound name will have the format: [ligand names in alphabetical order] followed by [central atom's name] followed by (central atom's oxidation state in roman numerals). Since we have 4 amines and 2 chlorides, we write: tetraammine dichloridorhodium. Finally, we must determine the oxidation state of rhodium. Rhodium has an oxidation state of +3 in this complex, as there are 2 chlorides with -1 charge each, resulting in +3 charge (considering 3 chloride ions in total). So, the complex name is: tetraammine dichloridorhodium(III) chloride. #b# Name compound \(\mathrm{K}_{2}[\mathrm{TiCl}_{6}]\)

Step 1: Identify central atom and ligands

The central atom is Ti(titanium) and the ligands are six chloride ions (Cl\(^-\)). Additionally, there are two potassium ions (K\(^+\)) acting as counterions.

Step 2: Name the ligands and central atom

Since we have six \(\mathrm{Cl}^-\) ligands, they are named "hexachlorido" and the central atom Titanium will be named "titanate".

Step 3: Combine the ligand and central atom names, along with the appropriate oxidation state

The complex name follows the format mentioned earlier. The ligand name is hexachlorido. The central atom name is titanate(IV), as the total charge on titanium must equal the total charge from the 6 chlorides (-6). The name of the full compound is: potassium hexachloridotitanate(IV). #c# Name compound \(\mathrm{MoOCl}_{4}\)

Step 1: Identify central atom and ligands

The central atom is Mo(molybdenum) and the ligands are four chloride ions (Cl\(^-\)) and one oxide ion (O\(^{2-}\)).

Step 2: Name the ligands

Four \(\mathrm{Cl}^-\) ligands are named "tetrachlorido" and the O\(^{2-}\) ligand should be named "oxido".

Step 3: Combine the ligand and central atom names, along with the appropriate oxidation state

The complex name follows the format mentioned earlier, and is ordered alphabetically, becoming tetrachlorido-oxido. The total charge from the ligands is -6 + (-2) = -8, so the central atom oxidation state is +8, and the name of molybdenum in this case is molybdenum(VIII). Combined, the full name of the complex is tetrachlorido-oxido-molybdenum(VIII). #d# Name compound \([\mathrm{Pt}\left(\mathrm{H}_{2}\mathrm{O}\right)_{4}\left(\mathrm{C}_{2}\mathrm{O}_{4}\right)]\mathrm{Br}_{2}\)

Step 1: Identify central atom and ligands

The central atom is Pt(platinum) and the ligands are four water molecules (\(\mathrm{H}_2\mathrm{O}\)) and one oxalate ion (\(\mathrm{C}_2\mathrm{O}_4^{2-}\)). Additionally, there are two bromide ions (Br\(^-\)) outside the square brackets acting as counterions.

Step 2: Name the ligands

Four water ligands are named "aqua", and the oxalate ligand is named "oxalato".

Step 3: Combine the ligand and central atom names, along with the appropriate oxidation state

Following the format mentioned earlier, we name the complex "tetraaqua oxalatoplatinum" followed by the oxidation state of platinum in Roman numerals. Since we have a total of -4 charge from oxalate and -2 charge from the two bromides, the final complex name is tetraaqua oxalatoplatinum(II) bromide.