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Chemistry 2 > Chemistry Y2: Coordination Chemistry > Flashcards

Chemistry Y2: Coordination Chemistry Flashcards

1
Q

What are the 5 d orbitals

A

dxy, dxz, dyz, dz². dx²-y²

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2
Q

How many e can fit in d shell

A

2 e in each shell =10e

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3
Q

what is the electronic configuration of Cr

A

[Ar]4s1 3d5

Stable half shell takes priority

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4
Q

what is the electronic configuration of Cu

A

[Ar]4s1 3d10

Stable full shell takes priority

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5
Q

How do TMs exist in many oxidation states

A

Early TMs can lose all valence e

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6
Q

In metal/atom - ion coordination complexes which electrons are removed first 3d or 4s

A

4s

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7
Q

what bonds to TMs and ligands form?

A

Coordinative/ dative/ donor/ metal-ligand

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8
Q

Which is true?
TMs are Lewis acids
Ligands are lewis acids

A

TMs are lewis acids- accept e
Ligands are Lewis bases- donate e

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9
Q

what is a mono-dentate ligand?

A

A ligand that can only form a single coordinate bond with the metal centre

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10
Q

What is a Bi-dentate ligand?

A

A ligands that is capable of forming 2 coordinate bonds with a central metal ion

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11
Q

What is a poly-dentate ligand?

A

A ligands that can form multiple coordinate bonds with a central metal ion e.g. tetra-dentate

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12
Q

What 3 factors affect number of ligands in a complex

A
  1. Size of the atom
  2. Steric interactions between ligands
  3. Electronic interactions between metal and ligand = BONDING
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13
Q

What is structural isomerism in coordination complexes?

A

Same molecular formula, different order of bonds

*Ionisation isomerism
*Hydration isomerism
*Coordination isomerism
*Linkage isomerism

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14
Q

What is stereoisomerism in coordination complexes?

A

Same molecular formula/ sequence of bonds but different spatial arrangement

*Geometrical isomerism (Cis and Trans)

*Optical isomerism (Chiral centre)
e.g. [M(L-L)₃] , [M(L-L)₂] and (L-L chelate ligands)

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15
Q

What coordination does a 7-coordinate complex have

A

Pentagonal Bipyramidal
or
Square faced monocapped trigonal prism

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16
Q

What coordination does a 8-coordinate complex have

A

Square antiprism

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17
Q

What coordination does a 9-coordinate complex have

A

Square faced tricapped trigonal

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18
Q

What does chelate mean?

A

A bidentate ligand bonded to a single metal ion

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19
Q

How do ligands approach the metal ion? and why?

A

Along the X,Y and Z axis
So they’re evenly spaced

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20
Q

How Do ligands contribute to the spherical electrical field around the metal ion

A

Each ligand has its own electrical field which contributes to the spherical electrical field

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21
Q

How does the d orbital increase in energy and become destabilised?

A

The ligands are drawn towards the +ve metal ion causing the electrical fields to become smaller

Ligands become close enough to bond to the ion

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22
Q

If an orbital points at a ligand what happens?

A

The orbitals get destabilised. Raised in energy

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23
Q

If an orbital points between ligands what happens?

A

The orbitals are stabilised. Lowered in energy

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24
Q

What is the crystal field splitting energy (Δ0)

A

It’s the energy gap between the orbitals

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25
Q

In octahedral splitting which orbitals are shifted +3/5 Δ0

A

d͓x²-y² and dz² orbitals

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26
Q

In octahedral splitting which orbitals are shifted -2/5 Δ0

A

dxy, dxz, dyz orbitals

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27
Q

Octahedral splitting what are the orbitals labeled and how degenerate is each

A

Higher 5d = doubly degenerate =eg
Lower 5d = triply degenerate = t2g

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28
Q

How do you calculate CFSE

A

CFSE= (m x +3/5) + (n x -2/5)
m= no. e in eg
n= no. e in t2g

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29
Q

What configuration comes with HIGH spin

A

Low configuration

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30
Q

What configuration comes with LOW spin

A

Hight configuration

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31
Q

What is ligand field splitting a measure of?

A

Strength of the ligand

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32
Q

Which spin in Co(III) always

A

Low spin

Unless bonded to F

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33
Q

What does a larger CFSE mean for the size of electrical field?

A

Larger electrical field

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34
Q

Why do weaker ligands have a smaller CFSE?

A

The weaker ligands don’t have enough energy to lift the energy of eg as much

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35
Q

What is pairing energy

A

The energy required to flip and electron with a spin up e in the same orbital

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36
Q

Why in weak field is CFSE < pairing energy?

A

Makes it easier to promote e to the eg orbitals rathe than flipping e to pair electrons

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37
Q

Why in strong field is the CFSE > Pairing energy?

A

Easier to pair electrons than to raise them to eg

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38
Q

Is High spin weak field or strong field?

A

WEAK FIELD

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39
Q

Which d configurations can have either High spin and Low spin?

A

d4, d5, d6, d7

For the other configurations there is only 1 possibility

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40
Q

What makes a complex high spin or low spin?

A

The metal ion
The metal ion ox state
The ligands

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41
Q

what is the spectrochemical series in order of increasing Δ0

A

I-, Br-, SCN-, Cl-, F-, OH-, C2O4²⁻, OH2, NCS-, py, NH3, en, bipy, CN-, CO

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42
Q

As Δ0 increases, field strength increases
TRUE OR FALSE

A

TRUE

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43
Q

WHAT does HONC stand for

A

It’s a means to remember the electrochemical series
H<O<N<C

H= Halides
O= Oxygen
N= nitrogen
C=Carbon

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44
Q

What do the colours of coordination complexes relate to?

A

To the energy gap between t2g and eg
A certain energy gap relates to a specific colour

45
Q

How to coordination complexes have colour?

A

Electrons are excited by visible light energy. The colour is created by the transition from t2g to eg

46
Q

Equation for the energy gap between t2g and eg

A

λ(nm)=10^7/Δ0(CM^(-1))

47
Q

what is the complementary colour rule

A

Whatever colour is absorbed its complementary colour is reflected-this is the colour we see

48
Q

HOW DOES CFSE INCREASE WITH OX STATE?

A

-changes based on the metal
-Increased pull on ligands
-Greater e-e repulsion
=Greater CFSE

49
Q

How does CFSE increase down a group?

A

-Radius of metal ion increases
-Electronic repulsion increases
-Larger Δ0

50
Q

What makes a complex colourless?

A

A filled or half filled d subshell

e.g. Zn²⁺ (d10) or Mn²⁺ (d5 and typically white)

51
Q

That geometry is formed when 4 ligands approach a central metal ion?

A

TETRAHEDRAL

52
Q

In a cubic space where are the ligands located in tetrahedral complexes

A

At the corners

53
Q

The triply degenerate t2 orbitals in tetrahedral all point to where?

So dxy is closer to the ligand that dx-y²

A

the sides of the cube

54
Q

The double degenerate orbitals of e in tetrahedral geometry point to where?

A

the faces

55
Q

In tetrahedral geometry which orbitals are t2 and which are e? And what fraction of Δt are they?

A

t2g = +2/5 = dxy, dxz, dyz
eg = -3/5 = dz², dx²-y²

56
Q

Why is there no (g) in t2 and e in tetrahedral crystal field splitting

A

No g = cause there is no inversion symmetry

57
Q

Why are dxy, dxz, dyz raised in Δt?

A

Because these orbitals face the ligands- destabilising them = increased energy

58
Q

The 4 ligands all don’t exactly point at the ligands in tetrahedral. What is Δt as a fraction of Δo?

A

Δt = ~ 4/9 Δo
approx
less that half

59
Q

What is the Δt CFSE equation?

A

(m x +2/5) + (n x -3/5)
m= no. e in t2
n= no. e in e

60
Q

Are all tetrahedral geometries HIGH spin or LOW spin?

A

They’re all HIGH spin
=small splitting

61
Q

What is the order of orbitals from most destabilised to least in SQUARE PLANAR?

A
  1. dx²y²
  2. dxy
  3. dz²
  4. dxz, dyz
62
Q

In SP how do the ligands approach the metal ion?

A

Along the X axis

63
Q

Why is the dx²-y² orbital the most destabilised?

A

2 ligands along the x axis have been removed. But dx²-y² still point at a ligand- destabilising it

64
Q

Why is the dxy orbital in SP raised?

A

It is in plane with the ligands

65
Q

How do you calculate ΔSP looking at ΔSP splitting diagram?

A

difference between dx²-y² and (dxz and dyz)

66
Q

Does SP splittng favour HIGH spin or LOW spin?

A

LOW SPIN
-suited for heavier metals

67
Q

Which metal ions have SP geometry?

A

2nd and 3rd row d8 metal ions
Rh(I), Pd(II), Pt(II), Au(III)

*For 1st row ions SP isn’t guaranteed it depends on the strength of the ligand
-STRONG LIGAND =SP
-WEAK LIGAND = TETRAHEDRAL

68
Q

How would you differentiate between [NiCl⁴]²⁻ and [PdCl⁴]²⁻?
Both are 8d

A

[NiCl⁴]²⁻ is High spin TETRAHEDRAL and therefore has 2 unpaired e
[PdCl⁴]²⁻ is low spin SP and therefor has 0 unpaired e

  • this gives the 2 complexes different MAGNETIC MOMENTS which can distinguish them
69
Q

What is the linear crystal field splitting diagram

A

Ligands approach along z axis

  1. dz²
  2. dxz, dyz
  3. dxy, dx²y²
  • No ligands in xy plane
70
Q

6 coordinate crystal field splitting,
which orbitals are stanilised and destabilised?

A

Dx²y² and dz²= destabilised and degenerate
dxy, dxz, dyz = stabilised and degenerate

71
Q

Jahn -Teller effect
How do we decide where to put an e if 2 orbitals are degenerate?

A

We need to make them become non-degenerate

72
Q

How do we break degeneracy?

A

J-T effect
*We need to stabilise 1 d orbital relative to the other
*distortion
*by changing bond distance, by changing E REPULSION WITHIN THE LIGANDS

73
Q

what are the 2 ways we can achieve the Jahn-teller effect?

A
  1. The 2 ligands on the Z axis can move further away from the metal= increased bond distance
    -equatorial bonds get closer
    -Stabilising dz² relative to dx²y²
    -e added to dz² first
  2. 4 ligands in equatorial plane push back from the metal
    -lengthening these bonds
    -dx²y² stabilised relative to dz²
    -e added to dx²y² first
74
Q

What is the effect of breaking bond degeneracy?

A

*Changes the geometry -> tetragonal
*easier to move 2 ligands rather than 4
*Most distortions occur along x-axis - elongated TETRAGONAL as x-axis is stretched

75
Q

Which configurations apply to Jahn-Teller?

A

d9, Low d7, HIGH d4

All Cu(II) complexes, Low spin Co(II), High spin Mn(III) and CR(II)

76
Q

what does small distortion (e.g along Z axis) in octahedral complexes mean?

A

The bond distances arn’t altered that much
*dx²-y² is raised compared to dz²
*dxy is raised but not enough to be above dz²

77
Q

what does large distortion (e.g along Z axis) in octahedral complexes mean?

A

The bond distances are altered largely
*dx²-y² is raised compared to dz²
*dxy is raised above dz²

78
Q

If bond distortion happens too extremely in OCTAHEDRAL complexes what happens?

A

Ligands detach on that specific axis
*Gives 4 coordinate SP complex

79
Q

What distortion tendency does Cu have

A

*Lose an axial ligand
*Breaks degeneracy
*Forms a 5-coordinate SQUARE PYRAMIDAL complex

80
Q

Does Jahn-Teller increase or decrease stability of a complex

A

It increases stability as it allows e to be added at lower energy levels

81
Q

In J-T if geometry changes do we keep or change the electronic configuration

A

We keep the octahedral electronic configuration

82
Q

How do we know if it’s Jahn-Teller from the electronic configuration

A

if the electron count in eg is 1 or 3
-As eg orbitals need to become non-degenerate in these instances

83
Q

What techniques can be used to tell us more about the Jahn-teller effect?

A
  1. x-ray crystallography
  2. Electronic absorption spectra
    -A J-T distorted complex will have 2 peaks as the energy levels are NOT degenererate
84
Q

Why is the Jahn-Teller effect negligible when there is uneven occupancy of the t2g orbital

A

Because the orbitals point between the ligands

85
Q

even though J-T in negligible for t2g why do we sometimes see 2 peaks in electronic absorbtion

A

Caused by excited e jumping from t2g to either dx²-y² or dz²

86
Q

what are the 3 electronic configurations with we need to know for Jahn-Teller effect?

A

d9, Low d7, high d4

87
Q

what is the macrocyclic effect

A

*Involves rings of at lease 9 atoms with at least 3 donor atoms
*cyclic ligands are a lot more stable - they’re too rigid to dissociate arms to attach donor atoms
*They lock metal ions in enzymes and proteins
e.g. nitrogen donors

88
Q

what is denticity?

A

the number of donor atoms through which ligands bind

89
Q

What is chelation?

A

When 2+ donor atoms bind to a metal ion:
Formation of a chelate ring
5-membered ring is most stable

90
Q

What dictates if and x-membered ring is favourable

A

the bite angle varies depending on x
*Best bite angle is 5 membered
*Above 6 becomes unstable
*3 and 4 are unfavourable

91
Q

What conditions for entropy and enthalpy are needed to favour a chemical process

A

+ve change in entropy
-ve enthalpy

92
Q

what is Gibbs free energy?

A

How likely a chemical process is

ΔG°=–RTlnK=ΔH°–TΔS°

ΔG°= gibbs free energy of a reaction
ΔH = enthalpy of reaction
ΔS° = entropy of reaction
T = temp (K)
R = 8.314
K= equilibrium constant

93
Q

what is entropy and what is its relation to the chelate effect?

A

Entropy is an increase in disorder
*More favourable reaction = increase in disorder (ΔS°> 0)

If ΔS is more +ve, ΔG is more -ve

*CHELATE EFFECT WORKS BY REPLACING MONODENTATE LIGANDS WITH POLYDENTATE LIGANDS
-driven by increase in entropy

94
Q

What is supramolecular chemistry

A

How molecules interact with each other through non-covalent bonds
e.g.
Molecular recognition in DNA

Non-covalent bonds include:
*H-bonds
*Electrostatic force sof attraction
*Van derWaals
*Pi-Pi stacking
*matal-ligand bonds

95
Q

What do we get if we add 2 bipy ligands to Cu+?

A

TETRAHEDRAL COMPLEX in double helix
*Cu+ ensures bipys stay orthogonal to each other = Bite angle of 90⁰

96
Q

what do we get if we add 3 bipy ligands to Fe2+

A

A triple helix
Bipy ligands are orthogonal to each other

97
Q

How are molecular grids formed

A

2 terpy units combines with Fe2+
2 by 2 moleculare grid
Grid is planar

Multidentate ligands can have 2,3or 4 terpy pockets

but grids can only ever by 2’2, 3’3, 4’4 not mixed

98
Q

What is the molecular formular of magnetite/

A

Fe3O4

99
Q

what causes magnetism

A

Unpaired e

100
Q

What are the 2 types of magnetism? and which is bigger?

A

Paramagnetism&raquo_space; Diamagnetism

1.Paramagnetism- a material that aligns with a magnetic field because it has unpaired e

2.Diamagnetism- A substance without unpaired e and is repelled by a magnetic field

101
Q

What is spin angular momentum

A

*e rotates on its axis
*The electrons dipole has 2 orientations PARALLEL and ANIT-PARALLEL to the magnetic field

102
Q

What are the parallel and antiparallel spin quantum numbers?

A

Parallel =ms +1/2
Anti-parallel = ms -1/2

103
Q

in terms of energy, which is bigger parallel or antiparallel

A

Antiparallel&raquo_space; Parallel

104
Q

what are the 2 parts of the magnetic moment

A
  1. Apin angular momentum
  2. Orbital angular momentum
105
Q

what is orbital angular momentum? Give equation

A

the momentum given to the e while is circles the nucleus

μSo=√n(n+2)

μ= Magnetic moment
S = total spin

Spin only formula can be written in terms of n
n=Number of u unpaired e

106
Q

Why do paramagnetic compounds weigh more than diamagnetic compounds?

A

They’re repelled by the magnetic field

107
Q

Why are magnetic moments useful?

A

They can help distinguish between HIGH. and LOW configurations in octahedral complexes

108
Q

How to calculate total spin, S

A

S=n/2

where n= number of unpaired e

109
Q
A

Chemistry 2 (7 decks)

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