Question

What is the systematic name for each of the following ions? (a) \(\left[\mathrm{MnCl}_{4}\right]^{2-}\) (b) \(\left[\mathrm{Ni}\left(\mathrm{NH}_{3}\right)_{6}\right]^{2+}\) (c) \(\left[\mathrm{Co}\left(\mathrm{CO}_{3}\right)_{3}\right]^{3-}\) (d) \(\left[\mathrm{Pt}(\mathrm{en})_{2}(\mathrm{SCN})_{2}\right]^{2+}\)

Short answer

(a) Tetrachloromanganate(II) ion; (b) Hexaamminenickel(II) ion; (c) Tricarbonatocobaltate(III) ion; (d) Bis(ethylenediamine)dithiocyanatoplatinum(IV) ion.

Step-by-step solution

Name the Anion or Anionic Complex

For part (a), the complex ion is \( [\text{MnCl}_4]^{2-} \). The central metal is manganese, and it is present within the complex anion. In anions, the metal names end with the suffix '-ate.' The oxidation state of Mn here is +2, calculated by balancing the -1 charge of four chlorides with the overall -2 charge. So, the systematic name is tetrachloromanganate(II) ion.

Name the Cationic Complex

For part (b), the complex ion is \( [\text{Ni(NH}_3)_6]^{2+} \). The central metal is nickel, and ammonia ligands are named as 'ammine.' Since it is a cationic complex, the metal retains its normal name, "nickel," and the oxidation state of Ni is +2 (since each ammonia is neutral and the overall charge is +2). The systematic name is hexaamminenickel(II) ion.

Name the Anionic Complex with a Multi-Ligand

For part (c), the complex ion is \( [\text{Co(CO}_3)_3]^{3-} \). The central metal is cobalt within an anion. 'Carbonate' is the name for \(\text{CO}_3^{2-}\) ligands. Again, the '-ate' suffix applies for the anion. Calculate the oxidation state of Co by balancing 3 carbonate ions (each -2) with a -3 charge, resulting in Co(III). The systematic name is tricarbonatocobaltate(III) ion.

Name the Neutral and Charged Mixed Ligand Complex

For part (d), the complex ion is \( [\text{Pt(en)}_2(\text{SCN})_2]^{2+} \). The ligand 'en,' stands for ethylenediamine, a neutral bidentate ligand. 'Thiocyano' is the name for \(\text{SCN}^-\), given in its thiocyanate form. Platinum in the cationic complex retains its regular name. Determine Pt's oxidation state: 0 from 2 en ligands + 2 from thiocyanates, balancing to +4 alongside \(2+\) overall charge. The systematic name is bis(ethylenediamine)dithiocyanatoplatinum(IV) ion.

Key concepts

Systematic Nomenclature

Systematic nomenclature in coordination chemistry ensures that chemical names accurately represent the structure and composition of a compound. This process enables scientists to determine the identity and properties of the compound simply by reading its name. For coordination complexes, naming typically follows a set of rules standardized by IUPAC (International Union of Pure and Applied Chemistry). Here are some key aspects:

• The name begins with naming the ligands, followed by the central metal atom or ion.
• Ligands are listed alphabetically, with prefixes used for multiple identical ligands (e.g., di-, tri-, tetra-).
• The oxidation state of the central metal ion is indicated in Roman numerals in parentheses.
• For anionic complexes, the suffix '-ate' is added to the stem name of the metal.

These rules help to maintain clarity and consistency in chemistry communications. Using systematic nomenclature, chemists worldwide can understand and convey complex structures accurately.

Transition Metal Complexes

Transition metal complexes consist of a central metal atom or ion surrounded by molecules or anions, known as ligands. Transition metals are well-suited for forming complexes due to their partially filled d-orbitals. These complexes are notable for their:

• Variable oxidation states, which enable metals to form various stable configurations.
• Richly colored compounds, a result of d-electron transitions.
• Catalytic properties, which make them useful in industrial and biological processes.

In the context of the given examples, each complex is composed of a transition metal (Mn, Ni, Co, Pt) and different ligands, influencing the overall charge and stability of the complex. Understanding transition metal complexes is fundamental to exploring both inorganic chemistry and bioinorganic chemistry.

Oxidation States

Oxidation states indicate the degree of oxidation of an atom in a compound. They are essential in determining the formula and systematic nomenclature for complexes. In coordination chemistry, the oxidation state of the metal can impact the properties and reactivity of the complex.To calculate the oxidation state of a metal in a complex, consider:

• The charge of the entire complex.
• The charge contributions from each ligand (e.g., chloride -1, ammonia neutral).
• The balancing requirement with the overall charge of the complex.

For instance, in the complex \([ ext{MnCl}_4]^{2-}\), manganese must be +2 to balance the four chloride ligands' -1 charges, with the -2 overall charge of the complex. Recognizing oxidation states allows chemists to predict reactivity patterns and stability within the coordination compounds.

Ligand Naming

Ligands are ions or molecules that donate pairs of electrons to the central metal atom or ion in a complex. Correct naming of ligands is paramount in systematic nomenclature. Some key points about ligand naming include:

• Neutral ligands like ammonia are often given special names, such as 'ammine.'
• Anionic ligands often retain their original names but may necessitate a prefix "o" or "ato" suffix, such as "chloro" or "carbonato."
• Bidentate or polydentate ligands, such as ethylenediamine, are named with prefixes like "bis," "tris" for efficiency and clarity.

In our given examples, ligands like chloride ( ext{Cl}^-), ammonia ( ext{NH}_3), carbonate ( ext{CO}_3^{2-}), and thiocyanate ( ext{SCN}^-) each have specific names that must be included when identifying the chemical name of a complex. Proper ligand naming aids in constructing the correct systematic name of a coordination compound.