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Chemistry 2Y > Coordination Chemistry > Flashcards

Coordination Chemistry Flashcards

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1
Q

What are the 5 d-orbitals?

A

dxy
dyz
dxz
dz^2
dx^2 - dy^2

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2
Q

Which 4 d-orbitals are similarly shaped?

A

dxy
dyz
dxz
dx^2-dy^2

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3
Q

What is the shape of the 4 similarly shaped orbitals?

A

They are all clover shaped, but oriented on different planes

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4
Q

What is the shape of dz^2?

A

A dumbbell shape with donut shaped electron cloud around the centre

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5
Q

How can you deduce the number of electrons in d-orbitals of an ion?

A

Subtract the oxidation state from the group number of the element

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6
Q

Which is the Lewis acid, and which is the Lewis base between transition metals and ligands?

A

Transition metals = Lewis acid (accepts electrons)
Ligands = Lewis base (donates electrons)

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7
Q

How many lone pairs does Dien donate?

A

3 lone pairs (terdentate)

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8
Q

How many lone pairs does Tren donate?

A

4 lone pairs (tetradentate)

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9
Q

How many lone pairs does Porphyrin donate?

A

4 lone pairs (tetradentate)

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10
Q

How many lone pairs does EDTA donate?

A

6 lone pairs (hexadentate)

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11
Q

If a complex has CN 2, what is it’s structural geometry?

A

Linear

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12
Q

If a complex has CN 3, what is it’s structural geometry?

A

Trigonal planar

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13
Q

If a complex has CN 4, what is it’s structural geometry?

A

Tetrahedral or Square planar

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14
Q

If a complex has CN 5, what is it’s structural geometry?

A

Trigonal bipyramidal or Square pyramidal

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15
Q

If a complex has CN 6, what is it’s structural geometry?

A

Octahedral

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16
Q

What is the chelate effect?

A

Complexes of multidentate ligands have a greater stability than those of monodentate ligands

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17
Q

What is coordinative/ionisation isomerism?

A

Isomers that differ in which ligands are bonded to the metal, or which act as counterions (different transition metal but same ligands)

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18
Q

What is linkage isomerism?

A

Isomers that differ in which donor atom the ligands use to bond to the metal

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19
Q

Where does linkage isomerism occur, give two examples?

A

Linkage isomerism occurs in ambidentate ligands, in which there is more than one possible donor atom.
For example:
Cyanato ligand (OCN-) and NO2- ligand can both be O or N bonded

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20
Q

What is stereoisomerism?

A

Isomers in which the same ligands are bonded to the metal, but in different spacial arrangements

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21
Q

Which structural geometries can have cis/trans isomerism?

A

Square planar and octahedral species can have cis/trans isomerism

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22
Q

When does facial/meridional structural isomerism occur?

A

In octahedral complexes where there are two sets of monodentate ligands

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23
Q

What does a fac isomer look like?

A

Where 3 same ligands are on the octahedral face, which looks like all on the bottom right hand side of the metal, and the other 3 are on the top left.

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24
Q

What does a mer isomer look like?

A

Where 3 same ligands are on the octahedral meridial, which looks like two on the right and one bottom left, and the other 3 same are in the other positions

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25
Q

In what 2 complexes would you find chirality (and hence enantiomers)?

A
  • In octahedral complexes with three bidentate ligands
  • In octahedral complexes with two bidentate ligands and one monodentate ligand, the cis molecule is chiral
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26
Q

What is the name of the lower energy orbitals, and what orbitals are at this energy level (oct)?

A

t2g:
- dxy
- dyz
- dxz

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27
Q

What is the name of the higher energy orbitals, and what orbitals are at this energy level (oct)?

A

eg:
dz^2
dx^2-y^2

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28
Q

What is the energy difference between t2g and eg called (oct)?

A

Delta octahedral

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29
Q

How will electrons fill the orbitals in high-spin configuration (oct)?

A

Electrons will enter eg before pairing in t2g

30
Q

How will electrons fill the orbitals in low-spin configuration (oct)?

A

Electrons will pair in t2g before entering eg

31
Q

If delta oct is greater than electron pairing energy (in t2g), what configuration will be favoured (oct)?

A

Low spin, so electrons will pair in t2g before entering eg

32
Q

What is the CFSE equation for oct?

A

(no. electrons in t2g x -2/5) + (no. electrons in eg x +3/5)

33
Q

On the colour wheel, what is the lowest energy colour, and what is the highest energy colour?

A

Red is the lowest energy, and it increases in energy counter-clockwise until you get to violet, which is the highest

34
Q

How does ligand strength correspond to the colour on the spectrochemical series?

A

The stronger the ligand, the higher the energy of the colour; so the strongest ligands correspond to purple/violet, and the weakest to red/orange

35
Q

How can you work out the colour of a compound from the strength of the ligand?

A

The colour of the compound will be opposite the corresponding colour to the ligand. For example:
CN- is a strong ligand that corresponds to purple/violet, and will hence produce a yellow/orange compound, as yellow is opposite purple on the colour wheel

36
Q

What possible reasons can cause a compound to appear colourless?

A
  • Filled (d-10) or half filled high spin (d-5), meaning there are no possible electrons to be excited
    Or
  • Very strong ligand field, meaning delta oct wave number is outside the visible spectrum
37
Q

What 3 factors affect delta oct value?

A
  • Strength of ligand (greater strength, greater delta oct)
  • Oxidation state (larger positive oxidation state, the greater delta oct)
  • Down a group (down the group = larger the radii, the greater delta oct)
38
Q

What is the higher energy group of orbitals called (tetra), and what orbitals are at this level?

A

t2:
- dxy
- dyz
- dxz

39
Q

What is the lower energy group of orbitals called (tetra), and what orbitals are at this level?

A

e:
- dz^2
- dx^2 -y^2

40
Q

Why are the t2 orbitals higher energy (tetra)?

A

Because the orbitals (dxy, dyz, dxz) sort of point at the ligands, making them destabilised

41
Q

Why are the e orbitals lower energy (tetra)?

A

Because the orbitals (dz^2, dx^2-y^2) point between the ligands, making them more stable

42
Q

What is the difference between e and t2g called (tetra)?

A

Delta tetrahedral

43
Q

What is the delta tetrahedral value wrt delta octahedral?

A

Delta tetrahedral = 4/9 delta oct

44
Q

What is the CFSE equation for tetrahedral splitting?

A

CSFE = (no. electrons in t2 x +2/5) + (no. electrons in e x -3/5)

45
Q

What is the configuration of tetrahedral complexes and why?

A

Tetrahedral complexes are always high spin, as the delta T is small, so it is pairing energy in e is greater than delta T.
This means electrons always enter t2 before pairing in e

46
Q

In square planar geometry, what is most destabilised orbital and why?

A

dx^2 -y^2 is the most destabilised, as it points at all four ligands

47
Q

In square planar geometry, what is second most destabilised orbital and why?

A

dxy is the second most destabilised, as it is in the same plane as the ligands

48
Q

What is the crystal field splitting of square planar complexes?

A

dx^2-y^2
dxy
dz^2
dxy dyz

2 1 1 1

49
Q

For what transition metals does square planar geometry occur?

A

For 4d8 and 5d8 transition metals.
For it to occur in 3d8 metals, a strong field ligand is required

50
Q

How is square planar configuration different to tetrahedral?

A

Tetrahedral complexes = always high spin
Square planar complexes = usually low spin

51
Q

How can you differentiate tetrahedral and square planar complexes experimentally?

A

By measuring the magnetic moment.
Tetrahedral complexes will have a higher magnetic moment, as there are more unpaired electrons

52
Q

What is the Jahn Teller effect?

A

When degeneracy of orbitals is broken; one d orbital is stabilised relative to the other

53
Q

For what octahedral complexes does Jahn Teller distortion occur?

A

d9
low spin d7
high spin d4

54
Q

What can a larger Jahn Teller distortion result in for octahedral complexes?

A

A larger enough distortion will result in 2 ligands detaching from the metal, resulting in a 4 coordinate square planar complex

55
Q

What does Cu (II) have a tendency to become due to the Jahn Teller effect?

A

Cu (II) has a tendency to become a 5-coordinate complex by losing one ligand along the z-axis (to break the degeneracy).
The result of this is a square pyramidal complex

56
Q

How can Jahn Teller distortion be measured?

A

By measuring bonds lengths through crystallography. The greater the difference in absorption peaks, the greater the distortion

57
Q

Is Jahn Teller effect present in t2g?

A

Yes, but it is negligible as the orbitals point inbetween ligands

58
Q

What is the most stable chelate ring?

A

5 membered chelate rings (such as ox2-) are the most stable

59
Q

What do 4 or >6 membered rings tend to form?

A

They tend to bridge two metal atoms

60
Q

What is a macrocycle?

A

A ring of at least 9 atoms, with at least 3 donor atoms

61
Q

What is the macrocyclic effect?

A

Macrocyclic complexes are far more stable

62
Q

What are the two types of magnetism?

A

Paramagnetic- attracted by a magnetic field (i.e unpaired electrons present)
Diamagnetic- repelled by a magnetic field (i.e. no unpaired electrons present)

63
Q

What is a larger force out of para and dia magnetism?

A

Paramagnetism is a much larger force than diamagnetism

64
Q

What is ferromagnetism?

A

A form of paramagnetism, in which the alignment of unpaired electrons extends throughout the material, making it a permanent magnet

65
Q

What are the two possible ms values of electrons in a magnetic field?

A

+1/2 or -1/2

66
Q

What is the orientation of +1/2 electrons?

A

+1/2 ms electrons will be aligned with the magnetic field

67
Q

What is the orientation of -1/2 eletrons?

A

-1/2 electrons will be aligned against the magnetic field

68
Q

Which have a higher energy out of +1/2 and -1/2 ms electrons?

A

-1/2 electrons have a higher energy2

69
Q

What is the formula to work out magnetic moment?

A

square root of: no. unpaired electrons x (no. unpaired electrons + 2)

70
Q

What is the unit of magnetic moment?

A

B.M.

71
Q

What can you use magnetic moment to deduce?

A

Whether it is a high or low spin complex.
From this you can also deduce complex geometry

72
Q

What is the only ligand that can push Co2+ into a square planar geometry?

A

CN-
[Co(CN)4]2- is square planar

Chemistry 2Y (7 decks)

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