Problem 53 - Chemistry The Molecular Science

Question

Give the charge on the central metal ion in each of these. (a) \(\left[\mathrm{VCl}_{6}\right]^{4-}\) (b) \(\left[\mathrm{Sc}\left(\mathrm{H}_{2} \mathrm{O}\right)_{3} \mathrm{Cl}_{3}\right]\) (c) \(\left[\mathrm{Mn}(\mathrm{NO})(\mathrm{CN})_{5}\right]^{3-}\) (d) \(\left[\mathrm{Ni}(\mathrm{en})_{2}\left(\mathrm{NH}_{3}\right)_{2}\right]^{2+}\)

Step-by-Step Solution

Answer

(a) +2, (b) +3, (c) +2, (d) +2.

Step 1: Identify the Charge on Ligands

In each complex, determine the charges associated with the ligands.\- For (a) \(\left[\mathrm{VCl}_{6}\right]^{4-}\), each chloride \(\mathrm{Cl}^{-}\) is \(-1\).\- For (b) \(\left[\mathrm{Sc}(\mathrm{H}_{2}\mathrm{O})_{3}\mathrm{Cl}_{3}\right]\), \(\mathrm{H}_{2}\mathrm{O}\) is neutral and each chloride \(\mathrm{Cl}^{-}\) is \(-1\).\- For (c) \(\left[\mathrm{Mn}(\mathrm{NO})(\mathrm{CN})_{5}\right]^{3-}\), \(\mathrm{NO}\) is neutral and each cyanide \(\mathrm{CN}^{-}\) is \(-1\).\- For (d) \(\left[\mathrm{Ni}(\mathrm{en})_{2}\left(\mathrm{NH}_{3}\right)_{2}\right]^{2+}\), both ethylenediamine \(\mathrm{en}\) and ammonia \(\mathrm{NH}_{3}\) are neutral.

Step 2: Calculate the Total Charge from Ligands

Calculate the total charge contributed by the ligands.\- For (a), the total charge from ligands is \(-1 \times 6 = -6\).\- For (b), the total charge from ligands is \(-1 \times 3 = -3\).\- For (c), the total charge from ligands is \(-1 \times 5 = -5\).\- For (d), the total charge from ligands is \(0\) since all ligands are neutral.

Step 3: Determine the Overall Complex Charge

Identify the overall charge of the complex from the problem statement.\- (a) \(-4\)\- (b) Neutral, so the charge is \(0\).\- (c) \(-3\)\- (d) \(+2\)

Step 4: Calculate the Charge on the Central Metal Ion

Use the formula: \[\text{Charge on metal ion} = \text{Overall complex charge} - \text{Total ligand charges}\]- For (a), Charge on V: \(-4 - (-6) = +2\)- For (b), Charge on Sc: \(0 - (-3) = +3\)- For (c), Charge on Mn: \(-3 - (-5) = +2\)- For (d), Charge on Ni: \(+2 - 0 = +2\)

Key Concepts

Charge of Central Metal Ion

In coordination chemistry, understanding the charge of the central metal ion is crucial. It helps in determining how the metal interacts within the complex. The charge on the metal ion can be calculated by considering both the overall charge of the compound and the charges contributed by the ligands.

To find the charge on the central metal ion, use the formula: \[ \text{Charge on metal ion} = \text{Overall complex charge} - \text{Total ligand charges} \]
This involves a simple arithmetic operation. For example, in the complex \( \left[\mathrm{VCl}_{6}\right]^{4-} \), the overall charge is \(-4\), and the total charge of the ligands is \(-6\). Thus, the charge on vanadium is calculated as follows:

• Charge on V: \(-4 - (-6) = +2\)

Understanding these calculations aids in predicting the behavior and reactivity of the complex.

Ligand Charge

Ligands play a vital role in coordination chemistry by donating electron pairs to the central metal ion and stabilizing the complex. Each ligand can either be neutral or charged, which affects the overall charge of the compound.

When working with coordination compounds, it's essential to determine the charge on each ligand:

• Chloride \(\mathrm{Cl}^{-}\): \(-1\)
• Water \(\mathrm{H}_2\mathrm{O}\): Neutral \(0\)
• Cyanide \(\mathrm{CN}^{-}\): \(-1\)
• Ethylenediamine (en) and Ammonia \(\mathrm{NH}_3\): Neutral \(0\)

For example, in \( \left[\mathrm{Sc}(\mathrm{H}_{2}\mathrm{O})_{3}\mathrm{Cl}_{3}\right] \), the charge from the chloride ligands is \(-1 \times 3 = -3\), with water contributing \(0\).
This understanding is key to solving the overall charge of coordination compounds.

Transition Metals

Transition metals are elements found in the middle of the periodic table, notable for their ability to form various oxidation states and complex compounds. They often serve as the central metal ions in coordination chemistry due to their d-orbital electrons.

The unique properties of transition metals include:

• Multiple possible oxidation states
• Formation of colored compounds
• Ability to bind with various ligands

Take manganese in \( \left[\mathrm{Mn}(\mathrm{NO})(\mathrm{CN})_{5}\right]^{3-} \) for example. Manganese can present different oxidation states, which must be calculated by considering the known ligand charges and the overall compound charge.
This enriches the field of inorganic chemistry with diverse and interesting compounds.

Coordination Compounds

Coordination compounds are complex molecules consisting of a central metal ion bonded to one or more ligands. The arrangement and interactions within these compounds influence their chemical properties, including stability and reactivity.

Key features of coordination compounds include:

• Central metal ion bonded to negatively charged or neutral ligands
• Distinct geometric preparations based on the number and type of ligands
• Crucial role in biological, industrial, and medicinal applications

In coordination compounds like \( \left[\mathrm{Ni}(\mathrm{en})_{2}(\mathrm{NH}_3)_{2}\right]^{2+} \), understanding the charge distribution between the metal and ligands is vital for interpreting their function and behavior.
Coordination chemistry provides insights into processes such as catalysis and molecular recognition.