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CHEM214 > Group 10 > Flashcards

Group 10 Flashcards

1
Q

What’re the main ores Nickel is commonly found as?

A

NiAs - Kupfernickel

NiS - millerite

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2
Q

What type of lewis acid is Ni considered as?

A

Considered as an intermediate Lewis acid - so found with both hard and soft bases

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3
Q

How is Ni isolated? (Pure Ni ore)

A

NiAs and NiS are converted to Ni2S3

Then roasted in air to give NiO + SO2

NiO then reduced by C (same as Fe) if not impure

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4
Q

How is Ni isolated? (Impure NiO)

A

Impure NiO can be refined electrolytically or through the MOND process.

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5
Q

What is the Mond process?

A

Impure Ni is reacted with 4 CO to give [Ni(CO)4]

This is distilled under vacuum

Heating to over 450K gives pure Ni (+ 4 CO which is recycled)

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6
Q

What’s an issue with the Mond process?

A

Produces [Ni(CO)4] - a volatile, colourless, covalent, VERY toxic liquid

  • does produce VERY pure nickel tho
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7
Q

What’re the uses of nickel?

A

Was used in cheap jewellery
Still used in coins - US.
Problems with dermatitis though

‘Raney nickel’ hydrogenation catalyst

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8
Q

What affects the colour of octahedral Ni(II) compounds?

A

Increasing CFSE causes higher energy colours.

Strong field ligands absorb red light, so colour is blue-shifted - larger splitting

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9
Q

How does atomic radius change across a period?

A

Atomic radius DECREASES across a period

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10
Q

What geometry does Ni(II) favour with weak field ligands?

A

Octahedral&raquo_space; Tetrahedral - Because of CFSE difference, small splitting.

Occurs for d8 and d3

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11
Q

What geometry does Ni(II) favour with strong field ligands?

A

Square planar

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12
Q

What colour are tetrahedral Ni(II) 4-coordinate complexes?

A

Green or blue - 3 d-d bands in red region

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13
Q

What colour are planar Ni(II) 4-coordinate complexes

A

Generally red or yellow - d-d bands usually all overlap in UV-blue region due to large crystal splitting of strong field ligands

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14
Q

Are tetrahedral Ni(II) complexes para or diamagnetic?

A

Paramagnetic - 2 unpaired electrons

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15
Q

Are square planar complexes para or diamagnetic?

A

Diamagnetic - Ni-Ni bond forms

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16
Q

Are 6-coordinate Ni(III) complexes stable?

A

No, all are unstable with respect to reduction to Ni(II)

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17
Q

Are nickel fluorides stable?

A

No, very unstable and highly oxidising

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18
Q

What’s significant about K3[NiF6]?

A

Low spin at 5K - J-T distorted. µeff = 1.7µB

But at room temp, µeff = 2.9µB - high spin

Suggests a thermal eqm between low/high spin forms

Called a spin-crossover complex

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19
Q

What’s the only known complex of Ni oxides?

A

NiO.OH

20
Q

What use does NiO.OH have?

A

Important as anode in Ni-Cd batteries & Li ion batteries

21
Q

What effect do chelating ligands have?

A

They make complexes more stable

Eg - das

22
Q

What’s significant about Ni(IV) complexes?

A

ALWAYS LOW-SPIN

23
Q

Why is Ni(IV) more common than Co(IV)?

A

Because Ni(IV) is d6 - so low-spin means all 6e- are paired

Co(IV) is d5 and hence high splitting energy if high spin and 1 unpaired e- if low spin - less stable.

24
Q

Why is [NiF6]2- low-spin when [CoF6]3- high-spin?

A

Higher oxidation state, so bigger ∆oct

All Ni(IV) complexes are low spin because of this

25
Q

What’s significant about Pd and Pt?

A

They’re both very rare metals

26
Q

How do Pd and Pt occur in nature?

A

Tend to concentrate in sulfides and arsenides - soft Lewis acids

27
Q

How are Pd and Pt extracted from impure ores?

A

Ore is smelted to give a Cu/Ni rich crude metal

Then refined electrolytically - cast into anodes and oxidised, cathode is pure Cu and is reduced from Cu2+ to Cu -any Ni2+ stays in solution

Insoluble ‘anode sludge’ contains all impurities; Pt metals and any Au/Ag if present

28
Q

How is Pd/Pt recovered from the ‘anode sludge’ in extraction?

A

Anode sludge is dissolved in aqua regia (3:1 mix of conc HCl : conc HNO3) forming their [MCl6]2- complexes.

Separated by fractional crystallisation - Pt complex less soluble

Pd is recovered by reducing (NH4)2.[PdCl6] with formic acid

Pt is recovered by heating to decompose (NH4)2.[PtCl6]

29
Q

What’re the uses of palladium?

A

Used as catalyst for syntheitic chemistry, C-C bond-forming.
- also as cat. Converter in cars

Jewellery & dentistry

30
Q

What’re the uses of platinum?

A

Jewellery & dentistry

Catalysts - cat. Converters w Rh
- nitric acid synthesis
- fuel cell catalyst

Crucibles for high temp chemical processing

31
Q

What properties do Pd/Pt(II) always have?

A

They’re d8 so ALWAYS square planar, diamagnetic - even with weak field ligands

32
Q

What complex is an exception to platinum group metals geometry?

A

PdF2 - which is octahedral and has 2 unpaired e- per Pd

Purple

33
Q

What’re the most important ligands within Pt group metals complexes?

A

Organometallic ligands; as they tend to form most stable complexes, due to Pd/Pt being ‘softer’ then Ni

34
Q

What is the rate of Pt(II) ligand substitution?

A

Slow - ‘inert’ to ligand substitution - ideal rate

Not as slow as Os

35
Q

What’s the difference between Ni(III) and M(III)?

A

Ni(III) are low spin d7 6-coordinate, fairly common

Pd(III) and Pt(III) are VERY rare

36
Q

How is ‘Wolfram’s red salt’ made?

A

Treat rate yellow [Pt(EtNH2)]2+ in water with Cl2

Deep red PtCl3.4EtNH2 is produced

37
Q

What’s the structure of ‘Wolfram’s red salt’?

A

Chain of alternating square planar Pt(II) and octahedral trans-Pt(IV)

Cl- ions H-bond to EtNH2 groups

38
Q

What common trend do 4d/5d metals show?

A

That they prefer even-number d^n configurations with no unpaired electrons

39
Q

What oxidation state is common for Pt but not for Pd?

A

Pt(IV) is common but Pd(IV) requires anionic ligands - [PdF6]2- is only known complex, Pt has many

40
Q

What MX4 halide complexes are known?

A

All PtX4 complexes are known

But only PdF6, [PdI6]2- has been made but never isolated

41
Q

What does Pd(V) require to be stable?

A

Needs either anionic ligands or very strong donors like Me-.

Complex needs to be either anionic or neutral

42
Q

What’s the problem with cat ionic Pd(IV) complexes?

A

They are easily reduced to Pd(II).

43
Q

How do Pt(IV) complexes compare to Pd(IV) complexes?

A

Pt(IV) complexes are much more common, even when cationic.
- also doesn’t require anionic ligands

Pd(IV) must have anionic / strong donor ligands (Me- or Cl-)

44
Q

How are P(IV) complexes usually made?

A

By either oxidation of Pt(II) complexes or substitution of [PtCl6]2-

45
Q

What aren’t there any oxidation states past 4+ for palladium?

A

Already high oxidation state, d6 low-spin which is VERY hard to disrupt filled t2g set.

46
Q

What does high temperature and high pressure fluoridation of PtCl2 result in?

A

Gives [PtF6]-

One of the strongest oxidising agents known

CHEM214 (7 decks)

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