Brainscape's Knowledge GenomeTM

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


See full index

aa The f-elements > Lanthanide Complexes > Flashcards

Lanthanide Complexes Flashcards

1
Q

What are formula of lanthanide halides

A
  1. LnX3
  2. All LnX3 are known except for Pm which hasn’t been attempted and possibly EuI3
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What are properties of LnX3

A
  1. Ionic
  2. Crystalline
  3. High melting point
  4. Apart from trifluorides are highly deliquescent (tendency to dissolve?)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What are the LnX3 structures indicative of

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

What size are lanthanides

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

What are the fluorides of larger lanthanides like

A
  1. The fluorides of the larger lanthanides LnF3 (Ln = La–Pm) adopt the ‘tysonite’ (LaF3) structure
  2. in which the Ln3+ is coordinated by nine F- (massive ions) in a tricapped trigonal prismatic arrangement, with a further two F- at a slightly longer distance.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What are the structures of smaller lanthanide fluorides

A
  1. Beyond promethium, all of the LnF3 have the YF3 structure which features eight close contacts and one longer Ln-F distance.
  2. This is a result of the decreasing size of Ln.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What happens to atomic radius across a period

A
  1. In general it decreases
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What happens to the coordination number of halides to lanthanides as you move acorss the table

A
  1. Lower coordinate number due to lanthanide contraction
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Describe the chlorides of La to Gd

A
  1. The halides from La to Gd adopt the nine coordinate UCl3 structure a tricapped trigonal prismatic arrangement
  2. which is like the structure of LaF3 but with the two more distant F- removed.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Describe TbCl3 structure

A
  1. TbCl3 has the eight coordinate PuBr3 structure (like the UCl3 structure but with one of the capping Cl- removed.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Describe the LnCl3 compounds following Tb

A
  1. The LnCl3 compounds of the lanthanides following Tb all have a six-coordinate AlCl3 structure.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What impact does the size of an anion have on the coordination number to a given Ln3+ ion

A
  1. The size of the anion is also important in determining the coordination number to a given Ln3+ ion,
  2. with decreasing coordination number seen for increasing ion radius.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Describe structure of LaBr3, CeBr3 and PrBr3

A
  1. LaBr3, CeBr3 and PrBr3 all have the (nine coordinate) UCl3 structure,
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Describe the structure of tribromides of Nd to Eu

A
  1. the tribromides of Nd to Eu adopt the (eight coordinate) PuBr3 structure.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Describe structure of LnBr3 structures after Eu

A
  1. The remaining LnBr3 have the six coordinate FeCl3 structure.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is a common Ln oxide

A
  1. Ln2O3
  2. Sesquioxides
17
Q

How can common sesquioxide Ln2O3 be made

A
  1. By heating lanthanide metals in air
  2. Or heating oxy-compounds such as nitrates or carbonate
18
Q

Give equation to show formation of Ln2O3 from nitrate

A
  1. 4Ln(NO3)3 –> 2Ln2O3 + 12 NO2 + 3O2
19
Q

What elements need an extra step in formation of Ln2O3 and what is it

A
  1. Ce, Pr, And Tb
  2. Form LnO2 (Ln4+) under heating of oxy-compounds
  3. Can be reduced to Ln2O3 with H2
20
Q

What structures can Ln2O3 be divided into

A
  1. 3 structural types
  2. A-type
  3. B-type
  4. C-type
21
Q

Describe A-type structure of Ln2O3

A
  1. Light Ln
  2. Unusual LnO7 capped-octahedra
22
Q

Describe B-type structure of Ln2O3

A
  1. Middle Ln
  2. LnO7 units - but smaller arrangement of them as smaller lanthanides
  3. 2 capped trigonal prisms
  4. 1 capped octahedron
23
Q

Describe C-type structure of Ln2O3

A
  1. Heavy Ln
  2. LnO6 units but not octahedra- reflection of lanthanide contraction
  3. Face and body - divacant cubic
24
Q

Which elements form LnO2

A
  1. Ce, Pr, Tb when burnt
  2. Ln4+
25
Q

Can you get tetravalent halides

A
  1. These are confined to the fluorides of Ce(IV), Pr(IV) and Tb(IV),
  2. however only CeF4 is thermally stable.
26
Q

Describe CeO2 colours

A
  1. CeO2 (Ceria) is white when pure but is usually pale yellow due to some sub-stoichiometry.
27
Q

What are uses of CeO2

A
  1. This is exploited in catalytic converters catalysing the oxidation of unburnt hydrocarbons and converting CO to CO2.
  2. A further application is as a thin film on the walls of ‘self-cleaning’ ovens in which it can prevent the build up of tarry deposits.
28
Q

What does the occurrence of dihalides relate to

A
  1. The Occurrence of dihalides parallels the high values for the third ionisation energy
  2. Depends upon the oxidizing power of the halogen (iodides most numerous!)
  3. They are subdivided into 2 classes
29
Q

What are the 2 classes of LnX2

A
  1. Metallic compounds
  2. Insulating salt-like dihalides
30
Q

Describe the metallic compounds subclass of LnX2

A
  1. La, Ce, Pr, Gd
  2. Metallic lustre and high conductivity
  3. very good reducing agents
31
Q

What is actual structure of metallic compounds

A
  1. Actually Ln3+ system
  2. Ln3+(X-)2(e-) with the odd electron in a conduction band - due to how reducing system is
  3. Overlap of 4f orbitals too inefficient to produce a conduction band - so it isn’t produced from them
32
Q

Describe Insulating salt-like dihalides LnX2

A
  1. Eu, Sm Yb (ones that have Ln2+ systems)
  2. [Xe]4fn+1 config is more stable consistent with Ln2+(X-)2 structures
  3. Not as reducing as metallic compounds
  4. All LnX2 are easily oxidized and liberate H2 from H2O (Except for EuX2 which is stable in aqueous solution.)
33
Q

How are the synthetically useful iodides of the ‘divalent’ lanthanides obtained

A
  1. (Sm,Eu,Yb)I2 are obtained from thermal decomposition of LnX3
  2. or by reaction of NH4I and the Ln metal in liquid NH3.
34
Q

How are the metallic dihalides prepared

A
  1. The metallic dihalides are typically prepared by comproportionation:
  2. Ln + 2LnX3 –> 3LnX2
35
Q

Describe divalent oxides of Lanthanides

A
  1. LnO of Nd, Sm, Eu and Yb may be prepared by reduction of Ln2O3 with the elemental lanthanide at high temperature (800-2000 oC).
  2. All four oxides have the NaCl structure.
  3. However, while EuO and YbO are insulating (i.e. genuine Ln2+ O2-),
  4. the lustrous golden yellow NdO and SmO are electrically conducting (have free e- in conduction band as actually Ln3+

aa The f-elements (11 decks)

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