Problem 59 - Chemistry The Molecular Nature of Matter

Question

Give IUPAC names for each of the following: (a) \(\left[\mathrm{Ni}\left(\mathrm{NH}_{3}\right)_{6}\right] \mathrm{Cl}_{2}\) (d) \(\left[\mathrm{Mn}(\mathrm{CN})_{4}\left(\mathrm{NH}_{3}\right)_{2}\right]^{2-}\) (b) \(\left[\mathrm{CrCl}_{3}\left(\mathrm{NH}_{3}\right)_{3}\right]^{-}\) (e) \(\mathrm{K}_{3}\left[\mathrm{Fe}\left(\mathrm{C}_{2} \mathrm{O}_{4}\right)_{3}\right]\) (c) \(\left[\mathrm{Co}\left(\mathrm{NO}_{2}\right)_{6}\right]^{3-}\)

Step-by-Step Solution

Answer

(a) Hexaamminenickel(II) chloride, (d) Diamminetetracyanomanganate(II), (b) Triamminetrichlorochromium(III) ion, (e) Potassium trioxalatoferrate(III), (c) Hexanitrocobaltate(III)

Step 1: Identify the Central Metal Atom

Locate the central metal in the compound's formula and determine its oxidation state using the charge of the ligands and the overall charge of the complex.

Step 2: Name the Ligands

Name the ligands in alphabetical order, using the appropriate prefixes for their quantity (di, tri, tetra, etc.) and use 'bis' for complex ligands containing a prefix already.

Step 3: Name the Central Metal

Write the name of the central metal. If the complex is an anion, end the metal name with the suffix '-ate'. For cationic complexes, use the normal metal name.

Step 4: Indicate Oxidation State of Central Metal

Indicate the oxidation state of the central metal in Roman numerals in parentheses immediately following the name of the metal.

Step 5: Name the Counter ions (if present)

Name the counter ions outside of the coordination complex, if there are any, after naming the complex.

Step 6: Combine all parts

Combine all previous steps to write the full IUPAC name for the complex.

Key Concepts

Coordination Chemistry

Coordination chemistry deals with chemical compounds known as coordination compounds or complex compounds. These interesting entities consist of a central metal atom or ion, often a transition metal, surrounded by molecules or anions called ligands. These ligands can donate pairs of electrons and are thus bound to the metal center through coordinate covalent bonds, forming a coordination complex.

The number of ligands attached to the metal is called the coordination number, and the spatial arrangement of the ligands is referred to as the coordination geometry. The properties and reactivity of coordination compounds are greatly influenced by these factors. The study of these compounds is not only fascinating but also essential, as they play crucial roles in various chemical reactions, catalysis, and have numerous applications in biochemistry, medicine, and materials science.

Understanding the basics of coordination chemistry is imperative for correctly identifying the structure of these compounds which sets the stage for correct IUPAC naming, a skill vital for clear communication in the field of chemistry.

Oxidation State Determination

In coordination compounds, the oxidation state of the central metal atom or ion reflects its degree of electron loss or gain relative to its elemental state. Determining this number is critical for naming the compound according to IUPAC guidelines.

To find the oxidation state, consider the known charge of the ligands and the overall charge of the complex. The sum of the oxidation state of the metal and the charges of the ligands should equal the total charge of the complex. For instance, if a complex has a neutral overall charge and is coordinated with ligands that all carry a negative charge, the metal must have a positive oxidation state that balances the negative charges.

The oxidation state is indicated with Roman numerals in parentheses following the metal name in the complex's name. This is not only a formality but gives insight into the metal's electron configuration and potential reactivity within the complex.

Ligand Nomenclature

When naming ligands within coordination compounds, there are specific rules and conventions to follow as per IUPAC guidelines. Ligands are named first, in alphabetical order, before the metal ion. Neutral molecules are named as the molecule itself, such as 'ammine' for NH₃. Negative ligands typically end in 'o', like 'chloro' for a Cl⁻ ion, and 'cyanido' for the CN⁻ ion.

If a ligand already has a numerical prefix in its name, or if the ligand is complex, 'bis', 'tris', 'tetrakis', etc., are used to indicate the number of such ligands in the complex to avoid confusion. For example, ethylenediamine becomes 'bis(ethylenediamine)'.

Understanding ligand nomenclature is crucial because the names dictate the complex's structure and the order of ligands within its IUPAC name, affecting potential reactivity and synthesis in the field of coordination chemistry.