Molecular orbital theory to consider CFSE

Question 1

do t2g orbitals form sigma bonds?

Answer 1

No, they arent the right symmetry, they remain at the same energy level left as non-bonding orbitals

Question 2

Why do t2g orbitals remain at the same energy level when considering sigma interactions with ligands?

Answer 2

because they are not the right symmetry to mix with the ligand orbitals, so stay at the same energy level as non bonding orbitals.

Question 3

Are t2g metal orbitals the right symmetry to mix with ligand orbitals when thinking about sigma bonds?

Answer 3

No, they are only the right symmetry for pi bonds

Question 4

What is the 18 electron rule?

Answer 4

There is stability associated with having 18e- since no anitbonding orbitals are occupied. But there are exceptions to this

Question 5

How does electronegativity of donor atoms affect the energy of orbitals created?

Answer 5

Electronegative ligands have lower energy orbitals, since electrons are held closer, lower energy means lower energy eg* orbitals are created and since the t2g stays in same place delta oct is smaller.

Question 6

Do electronegative ligands cause smaller or bigger splitting when considering sigma interactions?

Answer 6

Smaller, since they are lower in energy they create lower in energy eg* orbitals which are closer to the non bonding t2g so lower delta oct

Question 7

Does a pi donor ligand have filled or unfilled p orbitals?

Answer 7

Filled

Question 8

Does a pi acceptor ligand have filled or unfilled p orbitals?

Answer 8

Unfilled antibonding p orbitals.

Question 9

Do pi donor ligands stabilise a low or high oxidation state?

Answer 9

High oxidation state since can contribute electron density.

pi donor ligands decrease delta oct

Question 10

Do pi acceptor ligands stabilise a low or high oxidation state?

Answer 10

Low oxidation state since they can delocalise electron density in their empty orbitals
pi acceptor ligands tend to increase delta oct

Question 11

If the ligand is more electronegative is a sigma only system is the complex more likely to be low or high spin?

Answer 11

More likely high since more electronegative ligand with sigma bonding leads to smaller delta oct

Question 12

What effect do pi donor ligands have on molecular orbitals?

Answer 12

pi donation destabilises t2g* meaning its closer in energy to eg* so delta oct is smaller than sigma only complexes

Question 13

What effect fo pi acceptor ligands have on molecular orbitals?

Answer 13

Stabilise the t2g orbitals meaning they are further from eg* meaning bigger delta oct than sigma only and pi donor ligands

Question 14

Examples of pi acceptor ligands?

Answer 14

CN- and CO

Question 15

Are pi acceptor ligands strong or weak field ligands?

Answer 15

Strong field- cause big splitting

Question 16

Which is a strong field ligand, the pi donor or pi acceptor ligand?

Answer 16

The pi acceptor as it causes big splitting

Question 17

Why do cis and trans complexes differ? (MO theory))

Answer 17

Trans complexes compete for E- density

Question 18

are pi donor ligands likely to increase or decrease delta oct?

Answer 18

decrease

Question 19

are pi acceptor ligands likely to increase or decrease delta oct?

Answer 19

increase