CH612 - Ligand Field Theory

Question 1

Answer 1

Question 2

Answer 2

Question 3

Type of MO = symmetry of MO

Answer 3

Question 4

Answer 4

Question 5

Mixing ligand π charater (π-donor) into the t_2g set of orbitals in an O_h ligand field results in the t_2g set becoming more _________.

Bonding or Antibonding

Answer 5

Antibonding

(Ligand π orbitals are lower in energy than the t_2g set and therefore any mixing results in HOMO frontier orbitals being of antibonding character)

Question 6

Mixing ligand π charater (π-acceptor) into the t_2g set of orbitals in an O_h ligand field results in the t_2g set becoming more _________.

Bonding or Antibonding

Answer 6

Bonding

(Ligand π* orbitals are higher in energy than the t_2g set and therefore any mixing results in HOMO frontier orbitals being of bonding character)

Question 7

π-Donors_____∆_oh

Increase or Decrease

Answer 7

Decrease

Question 8

π-Acceptors_____∆_oh

Increases or Decrease

Answer 8

Increase

Question 9

π-Donor ligands are ligands with ________ π orbitals.

Answer 9

Full
(oriented in parallel to the M-L axis)

Question 10

π-Acceptor ligands are ligands with ________ π orbitals.

Answer 10

Empty
(oriented in parallel to the M-L axis)

Question 11

π-Donor ligands are ________ bases.

Answer 11

Lewis
(e.g. Cl^-, Br^-, O^2-)

Question 12

π-Acceptor ligands are ________ acids.

Answer 12

Lewis

Question 13

Ranking of ligands with π bonds by field strength?

Answer 13

π-acceptor ligand > π-donor ligand
(thus CO > OH_-)

Question 14

Ranking of ligands without π bonds by field strength?

Answer 14

By strength of σ overlap
(e.g. H_- has a strong σ overlap because of short bond length)

Question 15

The presence of π-bonds is a dominant factor on ________.

Answer 15

Ligand strength

(strength of ligands with simultaneous π and σ bonding is determined by the character of the π bond)

Question 16

Strength of ligands ____________ affect strength of M-L bonds.

Answer 16

Does not necessarily

Strong M-L bonds have large Δ_O value (more stable). Δ_O is also affected by the metal atom.