MChem Master of Chemistry Master of Chemistry: Inorganic Chemistry 2

Question 1

Which of the following best describes the trans influence in square planar complexes?

Accepted Answer

The thermodynamic weakening of the bond trans to a strong trans-influencing ligand

Answer

The trans influence is a ground-state (thermodynamic) effect whereby a strongly trans-influencing ligand weakens and lengthens the metal–ligand bond trans to itself.

Question 2

In the Ziegler–Natta polymerization mechanism, the role of the titanium center is best described as:

Accepted Answer

A Lewis acid that coordinates and inserts the olefin via a Cossee–Arlman mechanism

Answer

Titanium acts as a Lewis acidic metal center where the alkene coordinates and inserts into the Ti–C bond via the Cossee–Arlman migratory insertion pathway.

Question 3

Which crystal field parameter (Δ) ordering correctly reflects the spectrochemical series for the following ligands?

Accepted Answer

CN⁻ > NH₃ > Cl⁻ > I⁻

Answer

The spectrochemical series ranks ligands by field strength: CN⁻ (strong π-acceptor) > NH₃ (σ-donor) > Cl⁻ > I⁻ (weak-field halides).

Question 4

The Wade–Mingos–Lauher rules predict that a nido borane cluster has how many skeletal electron pairs relative to the number of vertices?

Accepted Answer

n+2 pairs for n vertices

Answer

Nido clusters follow the n+2 rule, meaning they have one more skeletal electron pair than a closo cluster of the same vertex count.

Question 5

Which technique is most diagnostic for distinguishing terminal, bridging, and face-capping carbonyl ligands in metal carbonyl clusters?

Accepted Answer

IR spectroscopy (ν(CO) stretching frequencies)

Answer

IR spectroscopy directly measures ν(CO) frequencies: terminal CO (~2000 cm⁻¹), bridging CO (~1800 cm⁻¹), and face-capping CO appear at progressively lower wavenumbers.

MChem Master of Chemistry Practice Test

MChem Master of Chemistry Practice Test

MChem Master of Chemistry Master of Chemistry: Inorganic Chemistry 2