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Core Chemistry 1 > Coordination Chemistry 1 > Flashcards

Coordination Chemistry 1 Flashcards

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1
Q

Transition Metal

A

An element with a partially filled d- (or f-) sub-shell in at least one common oxidation state.

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2
Q

Complex (or Coordination Compound)

A

Positively charged central ion (or possibly a neutral atom), an acceptor, surrounded in a symmetrical manner by a shell of ions or molecules called ligands.

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3
Q

Acceptor

A

electrophile or lewis acid

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4
Q

Ligand

A

nucleophile or lewis base

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5
Q

Monodentate (or Unidentate) Ligands

A

One donor atom - they can be neutral or anionic ligands

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6
Q

Bidentate Ligands

A

Two donor atoms

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7
Q

Tridentate Ligands

A

Three donor atoms

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8
Q

Tetradentate Ligands

A

Four donor atoms

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9
Q

Hexadentate Ligands

A

6 donor atoms - [EDTA] 4-

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10
Q

Chelation

A

Formation of complexes by chelate ligands - simultaneous binding of multiple donor atoms by forming rings around the central atom

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11
Q

Ambidentate Ligands

A

Ligands that can attach themselves to the other central metal atoms through different atoms

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12
Q

Bridging Ligand

A

A ligand attached to two or more, usually metallic, central atoms.

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13
Q

Coordination number

A

Number of ligand atoms directly bonded to the central metal in the complex.

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14
Q

Nuclearity

A

The number of central metal atoms in a complex

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15
Q

Isomers

A

Two or more different compournds having the same formula, but different structures.

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16
Q

Stereoisomers

A

different arrangements of atoms

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17
Q

Structural Isomers

A

different bonds between atoms

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18
Q

Conformational isomers

A

interconvertible by bond rotation

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19
Q

Configurational isomers

A

non-interconvertible by bond rotation

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20
Q

Optical Isomers: enantiomers

A
  • have the same atoms, same sets of bonds but differ in relative orientation of these bonds
  • non-superimposable mirror images
  • they have identical physical, chemical and spectral properties except for they interact differently with a chiral environment
  • they are optically active
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21
Q

Diastereoisomers

A

not mirror images

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22
Q

Ʌ

A

left-handed helix for optical isomerism in an octahedral complex with bidentate ligands

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23
Q

Δ

A

right-handed helix for optical isomerism in an octahedral complex with bidentate ligands

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24
Q

Resolution of optical isomers

A

A racemic mixture is separated into its two constituent enantiomers by converting the enantiomers into a mixture of diastereoisomers, which differ in physical properties and can therefore be separated (they have different solubilities).

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25
Q

Polarimeter

A

used to measure the angle of rotation of each enantiomer

  • the observed rotation is proportional to the amount of each enantiomer present
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26
Q

Coordination Isomerism

A

Form of structural isomerism in which the composition of the coordination complex ion varies.

  • Made up of both cationic and anionic complex ions
  • Neutral species are not allowed
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27
Q

Hydrate (solvent) Isomerism

A

Possible with water in or out of coordination sphere - the compounds differ by the number of solvent molecules directly bonded to the metal ion.

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28
Q

Ionisation Isomerism

A

Involves the exchange of ions inside and outside of the coordination sphere.

  • Made up of a complex ion and counter ion (counter ion must also be able to be a ligand)
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29
Q

Linkage Isomerism

A

Coordination compounds with the same composition but differ in their metal atom’s connectivity to a ligand (ambidentate ligands only)

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30
Q

OH 2 ligand

A

aqua

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31
Q

N 2 ligand

A

dinitrogen

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32
Q

O 2 ligand

A

dioxygen

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33
Q

NH 3 ligand

A

ammine

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34
Q

CO ligand

A

carbonyl

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35
Q

Cl - ligand

A

chloro (chlorido)

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36
Q

Br - ligand

A

bromo (bromido)

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37
Q

[SCN] - ligand

A

thiocyanato / isothiocyanato

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38
Q

OH - ligand

A

hydroxo (hydroxido)

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39
Q

CN - ligand

A

cyano (cyanido)

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40
Q

[NO 2 ] - ligand

A

nitro / nitrito

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41
Q

Greek derived prefix: 1

A

mono

42
Q

Greek derived prefix: 2

A

di

43
Q

Greek derived prefix: 3

A

tri

44
Q

Greek derived prefix: 4

A

tetra

45
Q

Greek derived prefix: 5

A

penta

46
Q

Greek derived prefix: 6

A

hexa

47
Q

Greek derived prefix: 7

A

hepta

48
Q

Greek derived prefix: 8

A

octa

49
Q

Multiplicative prefixes: 2

A

bis

50
Q

Multiplicative prefixes: 3

A

tris

51
Q

Multiplicative prefixes: 4

A

tetrakis

52
Q

Multiplicative prefixes: 5

A

pentakis

53
Q

Multiplicative prefixes: 6

A

hexakis

54
Q

How to achieve large negative values of gibbs free energy?

A

When K (equilibrium constant) is large - equilibrium lies on RHS.

The stronger the new M-L bond being formed.

55
Q

What does K 1 , K 2 , etc stand for?

A

Stepwise Stability Constants

56
Q

What does β mean for stability constants?

A

Overall Stability Constant

57
Q

What information does β give?

A

Large values of β indicate that the concentration of the complex is much larger than the concentration of its constituents.

58
Q

What value of β is thermodynamically stable?

A

β ≈ 10 8

59
Q

Overall stability constant for stable complexes?

A

log β > 0 (β > 1) i.e. ΔG° is -ve

60
Q

Overall stability constant for unstable complexes?

A

log β < 0 (β < 1) i.e. ΔG° is +ve

61
Q

How does statistical error impact equilibrium constants?

A

Successive equilibrium constants will decrease if there are no changes in geometry,

i.e. K 1 > K 2 > K 3 > 4 > K 5 > K 6

62
Q

How does sterics impact equilibrium constants?

A

Bulky ligands can hinder the approach of subsequent ligands

63
Q

How does electrostatic factors impact equilibrium constants?

A

Each successive replacement of a water ligand with an anionic ligand reduces the positive charge on the complex.

64
Q

How does geometry impact equilibrium constants?

A

Large differences in values occur when there is a change in geometry

65
Q

Chelation

A

formation of complexes by chelate ligands, simultaneous binding of multiple donor atoms by forming rings around the central atom.

66
Q

Chelate Effect

A

Chelate complexes are more stable than complexes with similar monodentate ligands due to higher stability constants.

67
Q

Why does chelation decrease gibbs free energy ?

A
  • Because similar ligands are being replaced, there is no effect on ΔH
  • Difference is ΔS as it creates more disorder
68
Q

Macrocyclic ligand

A

3 or more potential donors in a ring of at least 9 atoms.

69
Q

Macrocyclic effect

A

Stability constants for complexes of macrocyclic ligands are higher than those for their acyclic counterparts thus making more stable complexes.

70
Q

How does the macrocyclic effect decrease gibbs free energy?

A

It can be due to ΔH or ΔS

71
Q

Hard acids (acceptors)

A
  • non-polarisable cations
  • small radius
  • high effective nuclear charge
    (higher charge-to-radius ratio)
  • high energy LUMO
72
Q

Hard acids examples

A
  • most metals in normal oxidation states
  • H +
  • all electropositive metals (groups I, II, etc)
73
Q

Soft acids (acceptors)

A
  • more polarisable cations
  • larger radius
  • lower charge-to-radius ratio
  • lower energy LUMO than hard acids
74
Q

Soft acids examples

A
  • Cu (I), Rh (I), Ag (I), Au (I)
  • Pd (II), Pt (II), Cd (II), Hg (III), Au (III)
  • all d-block metals in M(0)
75
Q

Examples of borderline acids (acceptors)

A
  • Fe (II), Co (II), Ni (II), Cu (II)
  • Tl, Pb, Bi
76
Q

Hard bases (donors)

A
  • small
  • non-polarisable
  • electronegative
  • difficult to oxidise
  • low energy HOMO
77
Q

Soft bases (donors)

A
  • big
  • more polarisable
  • easier to oxidise
  • higher energy HOMO
78
Q

How are most stable complexes formed? (acids and bases)

A
  • complex of a hard acid with a hard base
  • complex of a soft acid with a soft base

LIKE GOES WITH LIKE

79
Q

What is crystal field theory (CFT)?

A

it describes the breaking of orbital degeneracy in transition metal complexes due to the presence of ligands

  • it describes the strength of the metal-ligand bonds
80
Q

Assumptions made in crystal field theory

A
  • central metal ion is the point positive charge
  • ligands are regarded as dipoles or anions
  • ligands are the point negative charges
  • ionic bonding from electrostatic forces between positive and negative charges

NO ORBITAL OVERLAP OR ELECTRON SHARING

81
Q

What orbitals are filled first for d-block complexes?

A

d orbitals are filled before s

82
Q

How do you calculate d n configuration?

A

d n configuration = Group no. - Oxidation State

83
Q

Hund’s Rule

A

if there is more than one degenerate orbital, electrons first occupy separate orbitals with parallel spins

84
Q

Pauli Exclusion Principle

A

no more than two electrons can occupy a single orbital

if two electrons occupy a single orbital the spins must be paired

85
Q

Pairing Energy, P

A

the energy penalty for pairing two electrons in a single orbital

(pairing energies of 4d and 5d metals tend to be lower than for 3d)

86
Q

When is an octahedral complex high spin?

A

Δo<P
if Δo is small, there isn’t much different between t 2g and e g

87
Q

When is an octahedral complex low spin?

A

Δo>P
when there is a large energy difference

88
Q

what sort of spin are 4d and 5d metal complexes?

A

low spin complexes

89
Q

Generally for tetrahedral complexes, what sort of spin do they have?

A

Pairing is more unfavourable than filling t 2 orbitals so tetrahedral complexes are usually high spin

90
Q

Factors affecting the magnitude of Δo

A
  • metal oxidation state
  • position in periodic table
  • the spectrochemical series of ligands
91
Q

How does metal oxidation state affect Δo?

A
  • as charge on metal increased, Δo gets larger
  • smaller sized, highly charged ions

thus smaller M-L bonds and stronger interactions and so stronger splitting
(ELECTROSTATIC EFFECT)

92
Q

How does the position on the periodic table affect Δo?

A

larger d orbitals have stronger interactions
(5d>4d>3d)

Δo (1st row) < Δo (2nd row) < Δo (3rd row)
(SIZE EFFECT)

93
Q

How can you distinguish between high spin and low spin complexes?

A

by their magnetic properties

look at the no. of unpaired electrons
diamagnetic: no unpaired electrons
paramagnetic: has unpaired electrons

94
Q

What causes distortions of structures in complexes?

A

asymmetric filling of the d-orbitals

95
Q

What structure do complexes with bulky ligands favour?

A

Tetrahedral structure due to the geometry having bigger bond angles

96
Q

What d n electron count shows both high and low spin?

A

d 6

97
Q

How can isomers be distinguished?

A

Using IR spectroscopy and X-ray crystallography

98
Q

How can isomers be distinguished by properties of the ligands?

A

1H NMR spectroscopy

99
Q

What do you use in the resolution of optical isomers?

A

Potassium sodium (+) tartrate

100
Q

Stepwise vs Overall stability constants

A

Stepwise stability constants are equilibrium constants given for each step of the process of ligand substitution.

The overall stability constant is the equilibrium constant of the overall reaction.

Core Chemistry 1 (8 decks)

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