MChem Master of Chemistry Master of Chemistry: Inorganic Chemistry 5

Question 1

The trans effect series in square planar Pt(II) complexes places H⁻ and CO at opposite ends to Cl⁻. What is the kinetic basis for the strong trans effect of CO?

Accepted Answer

CO is a strong π-acceptor that stabilizes the transition state for substitution trans to itself by delocalization of the metal's electron density

Answer

CO's strong π-acceptor character stabilizes the trigonal bipyramidal transition state for associative substitution by delocalizing excess electron density, lowering the activation barrier for the trans ligand.

Question 2

In bioinorganic chemistry, the enzyme nitrogenase reduces N₂ to NH₃. Which metal clusters are present in the active site of Mo-nitrogenase?

Accepted Answer

The P-cluster (Fe₈S₇) and the FeMo-cofactor (MoFe₇S₉C homocitrate)

Answer

Mo-nitrogenase contains the P-cluster (Fe₈S₇) for electron transfer and the FeMo-cofactor (MoFe₇S₉C with homocitrate) as the site of N₂ binding and reduction.

Question 3

Which property of f-block elements makes their coordination chemistry distinctly different from d-block elements?

Accepted Answer

f orbitals are largely core-like, shielded by outer 5d and 6s electrons, leading to predominantly ionic, electrostatic bonding with ligands

Answer

The 4f orbitals are radially contracted and shielded by outer shells, so f electrons participate little in bonding; lanthanide coordination chemistry is dominated by ionic, electrostatic interactions.

Question 4

A d⁶ octahedral complex is described as low-spin with a large Δo. Which statement about its magnetic and substitution behavior is correct?

Accepted Answer

It is diamagnetic with zero unpaired electrons and typically substitution-inert

Answer

Low-spin d⁶ fills all three t₂g orbitals (t₂g⁶ eg⁰), giving zero unpaired electrons (diamagnetic) and high CFSE that makes the complex kinetically inert toward substitution.

Question 5

In main-group chemistry, the concept of 'lone pair stereochemical activity' explains why SnCl₂ is bent while SnCl₄ is tetrahedral. Which model accounts for this?

Accepted Answer

VSEPR theory treats the lone pair as an electron domain that influences molecular geometry

Answer

VSEPR treats the lone pair on Sn in SnCl₂ as a sterically active electron domain, giving an AX₂E arrangement that results in a bent (V-shaped) molecule.

MChem Master of Chemistry Practice Test

MChem Master of Chemistry Practice Test

MChem Master of Chemistry Master of Chemistry: Inorganic Chemistry 5