Problem 47 - General Chemistry

Question

Write the IUPAC name for each of the following coordination compounds. a. \(\mathrm{K}_{3}\left[\mathrm{FeF}_{6}\right]\) b. \(\left[\mathrm{Cu}\left(\mathrm{NH}_{3}\right)_{2}\left(\mathrm{H}_{2} \mathrm{O}\right)_{2}\right]^{2+}\) c. \(\left(\mathrm{NH}_{4}\right)_{2}\left[\mathrm{Fe}\left(\mathrm{H}_{2} \mathrm{O}\right) \mathrm{F}_{5}\right]\) d. \(\left[\mathrm{Ag}(\mathrm{CN})_{2}\right]^{-}\)

Step-by-Step Solution

Answer

a. Potassium hexafluoroferrate(III) b. Diaquadiamminecopper(II) c. Ammonium aquapentafluoroferrate(III) d. Dicyanoargentate(I)

Step 1: Analyze the formula for compound (a)

The compound is \( \mathrm{K}_{3}\left[\mathrm{FeF}_{6}\right] \). It contains potassium as the counter ion, iron as the central metal, and fluoride as the ligand. Since there are 3 potassium ions, the overall charge of the complex ion \( [\mathrm{FeF}_{6}] \) must be 3− to balance the 3+ charge of potassium.

Step 2: Name the ligands and central metal for compound (a)

The ligand in \( [\mathrm{FeF}_{6}]^{3-} \) is fluoride, which is named fluoro. The central metal iron, having a charge of 3+, is named ferrate because the complex is anionic.

Step 3: Construct the IUPAC name for compound (a)

Combine the ligand and the central metal name. The oxidation state of iron is indicated in roman numerals. Hence, the name is Potassium hexafluoroferrate(III).

Step 4: Analyze the formula for compound (b)

The compound is \( \left[\mathrm{Cu}\left(\mathrm{NH}_{3}\right)_{2}\left(\mathrm{H}_{2}\mathrm{O}\right)_{2}\right]^{2+} \). It contains ammonia and water as neutral ligands, and copper as the central metal.

Step 5: Name the ligands and central metal for compound (b)

The ligands are neutral: ammonia is named ammine and water is named aqua. The central metal copper in its usual positive oxidation state (2+) retains the name "copper."

Step 6: Construct the IUPAC name for compound (b)

Combine the ligand names and then the central metal name, with the oxidation state in roman numerals. Ammonia comes before water alphabetically. Therefore, the name is Diaquadiamminecopper(II).

Step 7: Analyze the formula for compound (c)

The compound is \( \left(\mathrm{NH}_{4}\right)_{2}\left[\mathrm{Fe}\left(\mathrm{H}_{2}\mathrm{O}\right) \mathrm{F}_{5}\right] \). It contains ammonium as the counter ion, iron as the central metal, water and fluoride as ligands.

Step 8: Name the ligands and central metal for compound (c)

The ligands water and fluoride are named aqua and fluoro respectively. The central metal iron when in a negative complex is named ferrate. Iron has the oxidation state of 3+.

Step 9: Construct the IUPAC name for compound (c)

Combine the ligand names and then the central metal name, with the oxidation state in roman numerals. Aqua comes before fluoro alphabetically. Hence, the name is Ammonium aquapentafluoroferrate(III).

Step 10: Analyze the formula for compound (d)

The compound is \( \left[\mathrm{Ag}(\mathrm{CN})_{2}\right]^{-} \). It consists of silver as the central metal, and cyanide as the ligand.

Step 11: Name the ligands and central metal for compound (d)

Cyanide is named as cyano. The central metal silver, in an anionic complex, is named argentate. The oxidation state of silver is evident in its 1- charge.

Step 12: Construct the IUPAC name for compound (d)

Combine the ligand name and the central metal name, with the oxidation state in roman numerals. The name is Dicyanoargentate(I).

Key Concepts

Coordination Chemistry

Coordination chemistry revolves around the study of compounds that consist of a central metal atom or ion surrounded by molecules or anions, known as ligands. This branch of chemistry explores the nature of the bonds between the central metal and its surrounding ligands. These complexes can have diverse geometric configurations dependent on the number and types of ligands attached, influencing their physical and chemical properties.

In coordination compounds, ligands participate with the central metal through a form of bonding known as coordinate covalent bonding. Here, the ligands donate a pair of electrons to the metal, contributing to the formation of a stable complex. Understanding the number, type, and behavior of ligands helps in predicting the structure, reactivity, and properties of the coordination compound.

Transition Metal Complexes

Transition metal complexes are a subset of coordination compounds. They involve transition metals as the central metal ions bonded to ligands. Transition metals are elements found in the d-block of the periodic table, and they are distinguished by their ability to form various oxidation states and complex shapes.

These complexes exhibit a rich array of properties due to the availability of unpaired d electrons. Such properties include variable oxidation states, the formation of colored compounds, and the potential for catalysis. Transition metals often possess partially filled d orbitals, which can be involved in bonding, leading to unique magnetic and electronic properties. This versatility makes them crucial in both biological systems and industrial applications.

Chemical Nomenclature

Chemical nomenclature in the context of coordination chemistry aims to provide clear and systematic names for coordination compounds. The International Union of Pure and Applied Chemistry (IUPAC) has established specific rules for naming these compounds, ensuring consistency across the scientific community.

When naming coordination complexes, ligands are listed before the central metal in alphabetical order. Neutral ligands often retain their molecule names, such as "aqua" for water and "ammine" for ammonia, whereas anionic ligands end with an "-o" suffix, like "cyano" for cyanide. The oxidation state of the central metal ion is expressed in roman numerals within parentheses immediately following the metal's name. For example, in "Diaquadiamminecopper(II)," the name indicates the ligands "aqua" and "ammine," the metal "copper," and its oxidation state of 2.

Oxidation States

The concept of oxidation states is pivotal in understanding the composition and reactivity of coordination compounds. The oxidation state of the central metal ion in a complex determines how it interacts chemically within the compound and with other substances.

In a coordination compound, the oxidation state is determined by the charge on the central metal and its surrounding ligands. It is crucial in naming since IUPAC nomenclature requires these values to be specified. For example, in the compound "Potassium hexafluoroferrate(III)," the "(III)" denotes that iron has an oxidation state of +3.

• The oxidation state helps predict the number of electrons a metal ion can gain or lose.
• It aids in balancing chemical equations involving redox reactions.
• Determining oxidation states is integral to understanding the electronic structure of the metal ion.

Through its application, chemists can deduce the likelihood of compound formation and potential reactivity, making it a fundamental concept in coordination chemistry.