Crystal Field theory

Question 1

What are the higher energy orbitals in an Octahedral crystal field splitting diagram and what are their symmetry species?

Answer 1

dx2-y2 and dz2

eg

Question 2

What are the lower energy orbitals in an Octahedral crystal field splitting diagram and what are their symmetry species?

Answer 2

dxy, dxz and dyz

t2g

Question 3

What are the higher energy orbitals in an Tetrahedral crystal field splitting diagram and what are their symmetry species?

Answer 3

dxy, dxz and dyz

t2

Question 4

What are the lower energy orbitals in an Tetrahedral crystal field splitting diagram and what are their symmetry species?

Answer 4

dx2-y2 and dz2

e

Question 5

What fraction of delta O is delta T

Answer 5

Delta T = 4/9 delta O

Question 6

From lowest to highest what is the order of the D orbitals in a square planar crystal field?

Answer 6

dxz and dyz —> dz then dxy (may interchange) —> dx2-y2

Question 7

Why are tetrahedral complexes almost always low spin?

Answer 7

Delta is much smaller

Question 8

Why does splitting increase with oxidation state?

Answer 8

higher charge on metal —> more attraction to ligands —> shorter bond lengths —> more interactions between orbitals and ligand charge

Question 9

how does splitting change down a group?

Answer 9

Increases - delta smaller in 1st row complexes therefore have a tendency to be high spin

Question 10

Describe the lowest end of the electrochemical series giving examples of ligands that are there?

Answer 10

• Small delta values
• Pi-donor ligands

e.g. I-, Br- and Cl-

Question 11

Describe the highest end of the spectrochemical series giving examples of ligands that are there?

Answer 11

• High delta values
• Pi acceptor Ligands

e.g. CN- and CO-

Question 12

Describe the middle of the spectrochemical series giving examples of ligands that are there?

Answer 12

• Essentially no pi effect
• Sigma donors

e.g. H2O, NCS-, Py, NH3

Question 13

What is the effect of a pi donor ligand?

What kind of metal complex does it best stabilise?

Answer 13

• Form both pi and sigma donor interactions
• Delta O is reduces (t2g raised in energy)

-Stabilises high oxidation state complexes

Question 14

What is the effect of a pi acceptor ligand?

What kind of metal complex does it best stabilise?

Answer 14

• Delta O is increases (t2g lowered in energy)

-Stabilises low oxidation state complexes

Question 15

What is the formula for the octahedral site preference energy?

Answer 15

OSPF = CFSE(oct) - CFSE(tet)