MChem Master of Chemistry Master of Chemistry: Inorganic Chemistry 4

Question 1

The Cotton effect observed in circular dichroism (CD) spectroscopy of a chiral metal complex is most directly associated with:

Accepted Answer

Electronic transitions that have both electric and magnetic transition dipole moments of non-zero magnitude

Answer

The Cotton effect arises from electronic transitions that are simultaneously electric-dipole and magnetic-dipole allowed, which occurs in inherently chiral chromophores.

Question 2

In the Pauson–Khand reaction, what is the role of the cobalt carbonyl complex [Co₂(CO)₈]?

Accepted Answer

It coordinates the alkyne and mediates [2+2+1] cycloaddition with an alkene and CO

Answer

Co₂(CO)₈ coordinates to the alkyne forming a stable alkyne–dicobalt complex that then undergoes an intramolecular [2+2+1] cycloaddition with an alkene and one CO to give a cyclopentenone.

Question 3

Which of the following best describes the Jahn–Teller effect in a high-spin d⁴ octahedral complex?

Accepted Answer

Elongation along the z-axis due to unequal occupation of the eg orbitals

Answer

High-spin d⁴ gives an eg¹ configuration (one electron in dz² or dx²-y²), causing a first-order Jahn–Teller distortion that typically elongates the z-axis bonds.

Question 4

Perovskite oxides (ABO₃) are structurally tolerant of A- and B-site substitution. The Goldschmidt tolerance factor t is used to predict:

Accepted Answer

The degree of structural distortion from the ideal cubic perovskite

Answer

The tolerance factor t = (rA + rO)/[√2(rB + rO)] quantifies how well the ionic radii fit the ideal cubic structure; t < 1 leads to tilting of BO₆ octahedra.

Question 5

In organometallic chemistry, an agostic interaction refers to:

Accepted Answer

A 3c-2e C–H⋯M interaction where the C–H bond donates electron density to an electrophilic metal center

Answer

An agostic interaction involves intramolecular donation of a C–H bonding electron pair to a coordinatively unsaturated metal, forming a 3-center 2-electron bond.

MChem Master of Chemistry Practice Test

MChem Master of Chemistry Practice Test

MChem Master of Chemistry Master of Chemistry: Inorganic Chemistry 4