Question

Name the following complex ions. a. \(\mathrm{Ru}\left(\mathrm{NH}_{3}\right)_{5} \mathrm{Cl}^{2+}\) 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. \(\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{5} \mathrm{NO}_{2}^{2+}\) a. \(\mathrm{Ru}\left(\mathrm{NH}_{3}\right)_{5} \mathrm{Cl}^{2+}\) 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. \(\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{5} \mathrm{NO}_{2}^{2+}\)

Short answer

The short answer for the complex ion names are: a. Pentaamminechlororuthenium(II) or Pentaamminechlororuthenium(2+) b. Hexacyanidoferrate(II) or Hexacyanidoferrate(4-) c. Tris(ethylenediamine)manganese(II) or Tris(ethylenediamine)manganese(2+) d. Pentaamminenitrito-N-cobalt(III) or Pentaamminenitrito-N-cobalt(3+)

Step-by-step solution

a. Identify the components#a. \(\mathrm{Ru}\left(\mathrm{NH}_{3}\right)_{5} \mathrm{Cl}^{2+}\)

Central metal ion: Ru (Ruthenium) Ligands: \(\mathrm{NH}_{3}\) (5 of them) - Ammine (not Ammonia, as Ammine is the ligand form) \(\mathrm{Cl}\) (1 of them) - Chloro Charge: 2+

a. Name the complex ion#a. \(\mathrm{Ru}\left(\mathrm{NH}_{3}\right)_{5} \mathrm{Cl}^{2+}\)

Name: Pentaamminechlororuthenium(II) or Pentaamminechlororuthenium(2+)

b. Identify the components#b. \(\mathrm{Fe}(\mathrm{CN})_{6}^{4-}\)

Central metal ion: Fe (Iron) Ligands: \(\mathrm{CN}\) (6 of them) - Cyanido Charge: 4-

b. Name the complex ion#b. \(\mathrm{Fe}(\mathrm{CN})_{6}^{4-}\)

Name: Hexacyanidoferrate(II) or Hexacyanidoferrate(4-)

c. Identify the components#c. $\mathrm{Mn}\left(\mathrm{NH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{NH}_{2}\right)_{3}^{2+}$

Central metal ion: Mn (Manganese) Ligands: \(\mathrm{NH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{NH}_{2}\) (3 of them) - Ethylenediamine Charge: 2+

c. Name the complex ion#c. $\mathrm{Mn}\left(\mathrm{NH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{NH}_{2}\right)_{3}^{2+}$

Name: Tris(ethylenediamine)manganese(II) or Tris(ethylenediamine)manganese(2+)

d. Identify the components#d. \(\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{5} \mathrm{NO}_{2}^{2+}\)

Central metal ion: Co (Cobalt) Ligands: \(\mathrm{NH}_{3}\) (5 of them) - Ammine \(\mathrm{NO}_{2}\) (1 of them) - Nitrito (nitro [as ONO] or nitrito [as NO2]) Since N is attached to the metal ion, use nitrito-N Charge: 2+

d. Name the complex ion#d. \(\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{5} \mathrm{NO}_{2}^{2+}\)

Name: Pentaamminenitrito-N-cobalt(III) or Pentaamminenitrito-N-cobalt(3+)

Key concepts

Chemical Nomenclature

Understanding the chemical nomenclature of complex ions is an essential skill in chemistry, particularly in coordination chemistry. The systematic naming of chemical compounds - including complex ions - follows specific rules set by the International Union of Pure and Applied Chemistry (IUPAC).

For complex ions, the names of the ligands are listed before the name of the central metal ion. Ligands are named in alphabetical order regardless of their charge or the number of ligands present. Greek numeric prefixes (mono-, di-, tri-, etc.) indicate the number of each type of ligand in the complex. When the complex ion possesses an overall charge, the metal's name ends with '-ate' if it's an anion, and for cations, the metal keeps its usual name but is followed by its oxidation state in Roman numerals within parentheses.

For example, in the naming of \(\mathrm{Fe}(\mathrm{CN})_{6}^{4-}\), 'hexa-' is indicative of six cyanido ligands and the suffix '-ate' is used for the ferrate to convey the negative charge.

Coordination Chemistry

In coordination chemistry, coordination compounds consist of a central metal atom or ion bonded to surrounding molecules or ions, known as ligands. This field of study is rich with examples of how metal ions interact with donor atoms, forming coordination complexes, that can exhibit a variety of different geometries and properties.

The nature of the bond between the metal and the ligands is coordinate covalent, wherein the ligands donate a pair of electrons to form the bond. The number of ligands attached to the central metal ion is termed the coordination number, and the three-dimensional arrangement of the ligands around the central atom is known as the ligands' geometry or coordination polyhedron. These factors determine much about the complex's reactivity and properties.

Transition Metals

Complex ions often involve transition metals, which are elements found in the d-block of the periodic table. These metals, such as iron (Fe), cobalt (Co), or ruthenium (Ru), have the unique ability to form a variety of different complexes due to their capability to exhibit multiple oxidation states and to form coordinate covalent bonds with a wide array of ligands.

The variable oxidation states of transition metals allow flexibility in the types of compounds they can form. This is beautifully exemplified in coordination compounds, where the metal ion's ability to adopt different electron configurations leads to a wide range of colors, magnetic properties, and reactivity patterns. For instance, in the exercise, Fe appears as Fe(II) in the hexacyanidoferrate(II) ion.

Ligands

A ligand is an ion or molecule that forms a coordination complex with a metal by donating a pair of electrons. Ligands can be anions, neutrals, or rarely cations and they can attach to the metal through a single atom or multiple atoms, known as monodentate and polydentate (multidentate) ligands, respectively.

For example, the \(\mathrm{NH}_{3}\) in \(\mathrm{Ru}\left(\mathrm{NH}_{3}\right)_{5} \mathrm{Cl}^{2+}\) is a monodentate ligand called ammine (note the double 'm' to distinguish it from the gas ammonia). In contrast, ethylenediamine (en), a bidentate ligand, binds through two nitrogen atoms to manganese in tris(ethylenediamine)manganese(II). The prefix 'bis-' is used instead of 'di-' for bidentate ligands to avoid confusion.