Aspects of Transition metal chemistry applied to biological systems

Question 1

How does the bonding work between a metal and it’s ligand

Answer 1

The metal is the acceptor which forms a dative bond with the ligand donor

Question 2

Electrons from the metal-centre of the ligand interact with the electrons from the ligand
What does this result in?

Answer 2

Resulting in a repulsive interaction, as both sets of electrons are negative
This causes the 3d electrons to go up in energy

Question 3

What causes the further splitting of the 3d orbitals on this diagram?

Answer 3

The d-orbitals do not exist spherically in space, their charge is localised (i.e. tetrahedral, octehedral etc)
The arrangement in space affect how the orbitals split (i.e. an octehdral splitting is shown here)

Question 4

What does the d-splitting orbtial diagram look like for an elongated octehedron and why?

Answer 4

An elongate octehedron has less repulsion in the z-direction and hence those orbitals are lower in energy

Question 5

What does the d-orbital splitting diagram look like for a compressed octehedron?

Answer 5

A compressed octehedron has more repulsion in the z-direction, hence these orbitals are higher in energy

Question 6

4d and 5d metals are always…

Answer 6

…low spin

Question 7

What is the Irving Williams series?

Answer 7

The effect of varying the M(ll) central ion on the stabilities of transition metal complexes

Question 8

What drives the pattern of the Irving Williams series?

Answer 8

1) From Mn(II) to Zn(II) there is an increase in the effective nuclear charge (this is responsible for the general increase in stability seen on the graph)
2) There is extra stability from Fe(II) to Cu(II) from the general trend. This is from crystal field stabilisation energy (0ΔO, -0.4ΔO, -0.8ΔO, -1.2ΔO, -0.6ΔO, 0ΔO)
3) However Cu(II) is an anomaly is due to the Jahn-Teller effect. When a complex has spin and orbital degeneracy, the complex will distort to remove degeneracy and achieve lower energy - mainly effect Cu(II)

Question 9

Jahn teller results in what type of distortion for copper?

Answer 9

When a complex like Cu has a spin and orbital degeneracy, the complex will distort to remove degeneracy and achieve a lower energy axial distortion (elongation) to remove degeneracy
The en ligand binds in the xy plane hence why it has such great stability in the Irving Williams Series