Group 10

Question 1

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

Answer 1

NiAs - Kupfernickel

NiS - millerite

Question 2

What type of lewis acid is Ni considered as?

Answer 2

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

Question 3

How is Ni isolated? (Pure Ni ore)

Answer 3

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

Question 4

How is Ni isolated? (Impure NiO)

Answer 4

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

Question 5

What is the Mond process?

Answer 5

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)

Question 6

What’s an issue with the Mond process?

Answer 6

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

• does produce VERY pure nickel tho

Question 7

What’re the uses of nickel?

Answer 7

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

‘Raney nickel’ hydrogenation catalyst

Question 8

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

Answer 8

Increasing CFSE causes higher energy colours.

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

Question 9

How does atomic radius change across a period?

Answer 9

Atomic radius DECREASES across a period

Question 10

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

Answer 10

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

Occurs for d8 and d3

Question 11

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

Answer 11

Square planar

Question 12

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

Answer 12

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

Question 13

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

Answer 13

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

Question 14

Are tetrahedral Ni(II) complexes para or diamagnetic?

Answer 14

Paramagnetic - 2 unpaired electrons

Question 15

Are square planar complexes para or diamagnetic?

Answer 15

Diamagnetic - Ni-Ni bond forms

Question 16

Are 6-coordinate Ni(III) complexes stable?

Answer 16

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

Question 17

Are nickel fluorides stable?

Answer 17

No, very unstable and highly oxidising

Question 18

What’s significant about K3[NiF6]?

Answer 18

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

Question 19

What’s the only known complex of Ni oxides?

Answer 19

NiO.OH

Question 20

What use does NiO.OH have?

Answer 20

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

Question 21

What effect do chelating ligands have?

Answer 21

They make complexes more stable

Eg - das

Question 22

What’s significant about Ni(IV) complexes?

Answer 22

ALWAYS LOW-SPIN

Question 23

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

Answer 23

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.

Question 24

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

Answer 24

Higher oxidation state, so bigger ∆oct

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

Question 25

What’s significant about Pd and Pt?

Answer 25

They’re both very rare metals

Question 26

How do Pd and Pt occur in nature?

Answer 26

Tend to concentrate in sulfides and arsenides - soft Lewis acids

Question 27

How are Pd and Pt extracted from impure ores?

Answer 27

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

Question 28

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

Answer 28

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]

Question 29

What’re the uses of palladium?

Answer 29

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

Question 30

What’re the uses of platinum?

Answer 30

Jewellery & dentistry Catalysts - cat. Converters w Rh - nitric acid synthesis - fuel cell catalyst Crucibles for high temp chemical processing

Question 31

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

Answer 31

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

Question 32

What complex is an exception to platinum group metals geometry?

Answer 32

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

Question 33

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

Answer 33

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

Question 34

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

Answer 34

Slow - ‘inert’ to ligand substitution - ideal rate Not as slow as Os

Question 35

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

Answer 35

Ni(III) are low spin d7 6-coordinate, fairly common Pd(III) and Pt(III) are VERY rare

Question 36

How is ‘Wolfram’s red salt’ made?

Answer 36

Treat rate yellow [Pt(EtNH2)]2+ in water with Cl2 Deep red PtCl3.4EtNH2 is produced

Question 37

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

Answer 37

Chain of alternating square planar Pt(II) and octahedral trans-Pt(IV) Cl- ions H-bond to EtNH2 groups

Question 38

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

Answer 38

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

Question 39

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

Answer 39

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

Question 40

What MX4 halide complexes are known?

Answer 40

All PtX4 complexes are known But only PdF6, [PdI6]2- has been made but never isolated

Question 41

What does Pd(V) require to be stable?

Answer 41

Needs either anionic ligands or very strong donors like Me-. Complex needs to be either anionic or neutral

Question 42

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

Answer 42

They are easily reduced to Pd(II).

Question 43

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

Answer 43

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-)

Question 44

How are P(IV) complexes usually made?

Answer 44

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

Question 45

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

Answer 45

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

Question 46

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

Answer 46

Gives [PtF6]- One of the strongest oxidising agents known