Question

Name the following complex ions. a. \(\operatorname{Ru}\left(\mathrm{NH}_{3}\right)_{5} \mathrm{Cl}^{2+}\) b. \(\mathrm{Fe}(\mathrm{CN})_{6}^{4-}\) c. \(\mathrm{Mn}\left(\mathrm{NH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{NH}_{2}\right)_{3}^{2+}\) d. \(\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{55} \mathrm{NO}_{2}^{2+}\) e. \(\mathrm{Ni}(\mathrm{CN})_{4}^{2-}\) f. \(\mathrm{Cr}\left(\mathrm{NH}_{3}\right)_{4} \mathrm{Cl}_{2}^{+}\) g. \(\mathrm{Fe}\left(\mathrm{C}_{2} \mathrm{O}_{4}\right)_{3}^{3-}\) h. \(\mathrm{Co}(\mathrm{SCN})_{2}\left(\mathrm{H}_{2} \mathrm{O}\right)_{4}^{+}\)

Short answer

a. pentaamminechlororuthenium(II) b. hexacyanoferrate(IV) c. tris(ethylenediamine)manganese(II) d. pentaamminenitrocobalt(III) e. tetracyanonickelate(II) f. tetraamminedichlorochromium(III) g. tris(oxalato)ferrate(III) h. tetrakisaquodithiocyanatocobalt(III)

Step-by-step solution

Name the ligands and the central atom

The ligands are 5 ammine (NH₃) and 1 chloro (Cl). The central metal ion is Ruthenium (Ru). The complex has a charge of +2.

Name the complex ion

Since the complex ion is cationic, we name the ligands first followed by the name of the central metal ion. The name for this complex ion is: pentaamminechlororuthenium(II) b. \(\mathrm{Fe}(\mathrm{CN})_{6}^{4-}\)

Name the ligands and the central atom

The ligands are 6 cyanide (CN⁻). The central metal ion is Iron (Fe). The complex has a charge of -4.

Name the complex ion

Since the complex ion is anionic, we name the ligands first followed by the name of the central metal ion in '-ate' form. The name for this complex ion is: hexacyanoferrate(IV) c. $\mathrm{Mn}\left(\mathrm{NH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{NH}_{2}\right)_{3}^{2+}$

Name the ligands and the central atom

The ligands are 3 ethylenediamine (NH₂CH₂CH₂NH₂). The central metal ion is Manganese (Mn). The complex has a charge of +2.

Name the complex ion

Since the complex ion is cationic, we name the ligands first followed by the name of the central metal ion. The name for this complex ion is: tris(ethylenediamine)manganese(II) d. \(\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{5} \mathrm{NO}_{2}^{2+}\)

Name the ligands and the central atom

The ligands are 5 ammine (NH₃) and 1 nitro (NO₂). The central metal ion is Cobalt (Co). The complex has a charge of +2.

Name the complex ion

Since the complex ion is cationic, we name the ligands first followed by the name of the central metal ion. The name for this complex ion is: pentaamminenitrocobalt(III) e. \(\mathrm{Ni}(\mathrm{CN})_{4}^{2-}\)

Name the ligands and the central atom

The ligands are 4 cyanide (CN⁻). The central metal ion is Nickel (Ni). The complex has a charge of -2.

Name the complex ion

Since the complex ion is anionic, we name the ligands first followed by the name of the central metal ion in '-ate' form. The name for this complex ion is: tetracyanonickelate(II) f. \(\mathrm{Cr}\left(\mathrm{NH}_{3}\right)_{4} \mathrm{Cl}_{2}^{+}\)

Name the ligands and the central atom

The ligands are 4 ammine (NH₃) and 2 chloro (Cl). The central metal ion is Chromium (Cr). The complex has a charge of +1.

Name the complex ion

Since the complex ion is cationic, we name the ligands first followed by the name of the central metal ion. The name for this complex ion is: tetraamminedichlorochromium(III) g. \(\mathrm{Fe}\left(\mathrm{C}_{2} \mathrm{O}_{4}\right)_{3}^{3-}\)

Name the ligands and the central atom

The ligands are 3 oxalate (C₂O₄²⁻). The central metal ion is Iron (Fe). The complex has a charge of -3.

Name the complex ion

Since the complex ion is anionic, we name the ligands first followed by the name of the central metal ion in '-ate' form. The name for this complex ion is: tris(oxalato)ferrate(III) h. $\mathrm{Co}(\mathrm{SCN})_{2}\left(\mathrm{H}_{2} \mathrm{O}\right)_{4}^{+}$

Name the ligands and the central atom

The ligands are 2 thiocyanato (SCN⁻) and 4 aqua (H₂O). The central metal ion is Cobalt (Co). The complex has a charge of +1.

Name the complex ion

Since the complex ion is cationic, we name the ligands first followed by the name of the central metal ion. The name for this complex ion is: tetrakisaquodithiocyanatocobalt(III)

Key concepts

Complex Ion Naming

Understanding how to name complex ions is crucial in coordination chemistry. Complex ions consist of a central metal atom or ion bonded to several ligands. Naming these ions involves a specific set of guidelines for consistency and clarity.

For **cationic complex ions**, where the charge is positive, the name of the ligands must be written in alphabetical order followed by the name of the metal. For example, in \( ext{[Ru(NH}_3 ext{)}_5 ext{Cl]}^{2+}\), the ligands "ammine" and "chloro" are listed before the metal "ruthenium", resulting in the name pentaamminechlororuthenium. The oxidation state of the metal ion is indicated in Roman numerals in parentheses at the end of the name, such as ruthenium(II).

**Anionic complex ions** have a negative charge, and here, the metal is named with an '-ate' suffix, such as "ferrate" for iron or "nickelate" for nickel. Cyanide (CN⁻) ligands in metal complexes are named as "cyano". Hence, \( ext{[Fe(CN)}_6 ext{]}^{4-}\) becomes hexacyanoferrate(IV). It's important to follow these conventions to accurately communicate the complex's composition and charge.

Ligand Identification

In coordination chemistry, ligands are molecules or ions that bind to a central metal atom. Identifying and naming ligands correctly is the first step in naming complex ions.

**Common Ligands and Their Names**:

• Ammonia (NH₃) is referred to as "ammine."
• Cyanide ion (CN⁻) is called "cyano."
• Ethylenediamine (NH₂CH₂CH₂NH₂) is represented as "ethylenediamine."
• Oxalate (C₂O₄²⁻) is termed "oxalato."
• Water (H₂O) is described as "aqua."
• Thiocyanate ion (SCN⁻) is known as "thiocyanato."
• Chloride ion (Cl⁻) is mentioned as "chloro."

These names should always precede the central metal's name in the complex.

When coordination sequences include more than one of the same type of ligand, prefixes such as "di-", "tri-", or "tetra-" are used to signify the number of each ligand present.

Cationic and Anionic Complexes

Complexes in coordination chemistry can be classified as either cationic or anionic based on the overall charge of the complex ion.

**Cationic Complexes**: These have a net positive charge, like \( ext{[Mn(NH}_2 ext{CH}_2 ext{CH}_2 ext{NH}_2 ext{)}_3}^{2+}\). For such complexes, after naming the ligands, the metal’s name appears as it is, followed by the oxidation state number in parentheses. For example, tris(ethylenediamine)manganese(II).

**Anionic Complexes**: These complexes carry a negative charge, and here, the metal's name is modified with an '-ate' ending followed by its oxidation number. An example is \( ext{[Fe(C}_2 ext{O}_4 ext{)}_3}^{3-}\), which is named tris(oxalato)ferrate(III).

Understanding whether a complex is cationic or anionic dictates the suffix used for the metal name. This is a key detail since the charge influences both the chemical properties and the naming conventions of the complex.