Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

(2) Transition Metals > Coordination Complexes > Flashcards

Coordination Complexes Flashcards

1
Q

What did Alfred Werner identify?

A

He identified principle features of geometric structures
He observed a violet and a green compound with the same formula CoCl3.4NH3
1 chloride in each compound reacts with Ag+ to form AgCl
He proposed the reactive chloride is not bound to cobalt
CoCl2(NH3)4 Cl-
He proposed the six bonded group are arranged in a symmetric fashion around the cobalt

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What are the possible arrangements of the bonded groups around the cobalt - Werner

A 
The arrangements include planar hexagon which has 3 isomers
Trigonal prismatic (2 isomers)
Octahedral (2 isomers)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Which arrangement did Werner conclude?

A

He only isolate two compounds (octahedral only has 2 isomers), violet and green
Likely arrangement of 6 ligands is octahedral
This is correct

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is a chiral compound?

A

This is a complex that is non superimposable on its mirror image and has no internal plane of symmetry

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is geometric isomerism

A

A complex can adopt two different geometries

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Which geometries show isomerism?

A

Isomerism is possible in square planar complexes of the general formula MX2Y2 and when X and Y are different

Octahedral complexes MX4Y2 complexes exist as cis and trans geometric isomers

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Which geometries do not show isomerism

A

Tetrahedral complexes of the general formula MX2Y2 do not form geometric isomers as there is only one way the four ligands can be arranged

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Describe the cis and trans configuration of octahedral with formula MX4Y2

A

It is cis when the 2 Y atoms are adjacent
It is trans when the 2 Y atoms are adjacent

Cis is adjacent
Trans is opposite

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What can octahedral complexes [MX3Y3] exist as?

A

They can exist can mer and fac
Mer is where 3 of the ligands X/Y in the same plane
Fac is where 3 ligands X/Y are adjacent (triangular face)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What confirmed werners predictions?

A

Optical isomerism confirmed Werners - octahedral

Optical activity is determining if a compound is chiral (optically active)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What does en mean?

A

en= ethane-1,2-diamine

The ligand binds using both N donor atoms
A curve can represent the CH2CH2 bridges in the en ligand

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What does ^ and triangle mean?

A 
Triangle= right rotation
^= left rotation
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is an enantiomer?

A

This is the mirror image of a chiral molecule

They are non superimposable

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Why is chirality not important for coordination complexes?

A

This is because metal ligand bonds are labile

This means the ligands can break away and change places so the enantiomer undergoes racemisation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Why can bidentate ligand enantiomers be isolated where monodentate ligands cannot?

A

Mondentate ligand bonds are labile and so the enantiomers undergo rapid racemisation
Bidentate ligands are less labile so it is possible to isolate these enantiomers

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What are bidentate isomers distinguished by and what do they form?

A

Bidentate ligands form a helix
The enantiomer forming the right handed, clockwise helix is labelled triangle
The left handed anti-clockwise helix is labelled ^

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Why are trans complexes not chiral?

A

This is because they contain a mirror plane

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

How can you separate diastereoisomers?

A

They are separated by fractional distillation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

How can you separate a racemic mixture of 2 enantiomers?

A

+ Ba d-tatrate
- BaSO4
And they are separated

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What is geometric isomerism?

A

Geometric isomerism, also known as cis- trans isomerism or EZ isomerism is a form of stereoisomerism

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Do enantiomers have the same properties?

Do diastereoisomers have the same properties?

A

Diastereoisomers have different properties
Enantiomers have the same properties apart from
-reactivity with chiral reagents
- reaction with plane polarised light

22
Q

What is the most common coordination for d block complexes?

A

Six coordination is the most common for d block metals

The majority of 6 coordinate complexes are octahedral

23
Q

What are some important distortions of octahedral complexes?

A

Stretching or compressing
1) a 4 fold rotation symmetry which results in tetragonal distortion

2) a 3 fold rotation symmetry axis results in trigonal distortion

24
Q

Why are higher coordination numbers less common for 3d and more common for 4d and 5d?

A

The central metal atom is large and so can coordinate more than six ligands

25
Q

What is geometry is most common for 7 coordinate complexes?

A

Pentagonal bipyramidal?

26
Q

What is the most common geometry for 8 coordinate?

A

Square antiprismatic

Cubic geometry is possible but not observed due to greater ligand ligand repulsions

27
Q

What geometry is common for 2 coordinate complexes?

A

Linear

It is common for ions with low charge density

28
Q

What geometry is common for 3 coordinate complexes?

A

Trigonal planar but is rare

29
Q

What geometry is common for 4 coordinate complexes?

A

Tetrahedral or square planar

Tetrachloro complexes can adopt either depending on the nature of the metal ion

30
Q

When is tetrahedral favoured over square planar?

A

Tetrahedral is favoured when the central atom is small and the ligands are large

31
Q

When is the square planar confirmation observed?

A

Observed for metals with d8 configuration

32
Q

What isomerism can square planar show and why is this important?

A

Cis or trans

Cis-Pt(II) are useful in cancer therapy- bind to base of DNA
The trans is not active

33
Q

What geometry is common for 5 coordinate complexes?

A

Trigonal bipyramidal and square pyramidal

They are less common

34
Q

Why do 5 coordinate complexes often exist as intermediate geometries?

A

The energy difference between square pyramidal and trigonal bypyramidal is small

Ligands are fluxional- often change sites

35
Q

How do ligands attach to the metal ion?

A

Via coordinate bonds to the donor atom

36
Q

What is the denticity of a ligand?

A

This is the number of donor atoms that are coordinated to the metal ion

37
Q

What denticity are ligands with 2, 3 ,4,5,6 donor atoms?

A 
2 is bidentate 
3 is tridentate 
4 is tetradentate 
5 is pentadentate
6 is hexadentate

2+ are polydentate

38
Q

What does a bidentate ligand form when it coordinates to a metal ion?

A

Forms a chelate ring (5 or 6 memebered)

39
Q

What types of ligands are there?

A

Monoatomic anions
Polyatomic anions
Neutral molecules cations

40
Q

Why are soft metals dangerous?

A

Soft metal ions can bind to soft complexes in the body which is toxic

41
Q

What is porphyrin?

A

This is a macrocyclic ligand

It’s iron complex is present in haemoglobin

42
Q

What is EDTA?

A

A hexdentate ligand
It can bond strongly to metals so good in analytical chemistry and medicine
Treats metal poisoning

43
Q

What are hard metals and what do they bond to?

A

Hard metals carry a high charge or have a high charge density
Favouring forming bonds to ligands with small electronegative donor atoms (hard ligands)
This bond has a high degree of ionic character

44
Q

What is a hard ligand?

A

Ligands that have small electronegative donor atoms

45
Q

What are soft metals and what do they form bonds to?

A

Soft metals have a lower charge and tend to be larger and more polarisable
They form bonds to ligands that have larger more polarisable donor atoms (soft ligands)
The bond has a high degree of covalent character

46
Q

What is a soft ligand?

A

Ligands that have larger more polarisable donor atoms

47
Q

What do intermediate metals form bonds to?

A

They can form strong bonds to both hard and soft Ligands

48
Q

What do intermediate Ligands form bonds to?

A

They can form strong bonds to both hard and soft metals

49
Q

Describe the difference in polarisability in ligand donor atoms or metal ions?

A

Polarisability (experience a charge shift)

Hard centres are little affected
Soft centres are easily polarised

50
Q

Describe the bonding between hard/ hard and soft/soft

A

Affinities are high between centres of the same type
Hard/ hard have highly ionic bonds
Soft/ soft have partly covalent bonds

Using this you can predict the stability of complexes

51
Q

What are examples of hard and soft electron pair donors?

A

Hard= fluoride and negatively charged oxygen

Soft= thiolates and sulphides

(2) Transition Metals (8 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions