Group 10 Flashcards
What’re the main ores Nickel is commonly found as?
NiAs - Kupfernickel
NiS - millerite
What type of lewis acid is Ni considered as?
Considered as an intermediate Lewis acid - so found with both hard and soft bases
How is Ni isolated? (Pure Ni ore)
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
How is Ni isolated? (Impure NiO)
Impure NiO can be refined electrolytically or through the MOND process.
What is the Mond process?
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)
What’s an issue with the Mond process?
Produces [Ni(CO)4] - a volatile, colourless, covalent, VERY toxic liquid
- does produce VERY pure nickel tho
What’re the uses of nickel?
Was used in cheap jewellery
Still used in coins - US.
Problems with dermatitis though
‘Raney nickel’ hydrogenation catalyst
What affects the colour of octahedral Ni(II) compounds?
Increasing CFSE causes higher energy colours.
Strong field ligands absorb red light, so colour is blue-shifted - larger splitting
How does atomic radius change across a period?
Atomic radius DECREASES across a period
What geometry does Ni(II) favour with weak field ligands?
Octahedral»_space; Tetrahedral - Because of CFSE difference, small splitting.
Occurs for d8 and d3
What geometry does Ni(II) favour with strong field ligands?
Square planar
What colour are tetrahedral Ni(II) 4-coordinate complexes?
Green or blue - 3 d-d bands in red region
What colour are planar Ni(II) 4-coordinate complexes
Generally red or yellow - d-d bands usually all overlap in UV-blue region due to large crystal splitting of strong field ligands
Are tetrahedral Ni(II) complexes para or diamagnetic?
Paramagnetic - 2 unpaired electrons
Are square planar complexes para or diamagnetic?
Diamagnetic - Ni-Ni bond forms
Are 6-coordinate Ni(III) complexes stable?
No, all are unstable with respect to reduction to Ni(II)
Are nickel fluorides stable?
No, very unstable and highly oxidising
What’s significant about K3[NiF6]?
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
What’s the only known complex of Ni oxides?
NiO.OH
What use does NiO.OH have?
Important as anode in Ni-Cd batteries & Li ion batteries
What effect do chelating ligands have?
They make complexes more stable
Eg - das
What’s significant about Ni(IV) complexes?
ALWAYS LOW-SPIN
Why is Ni(IV) more common than Co(IV)?
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.
Why is [NiF6]2- low-spin when [CoF6]3- high-spin?
Higher oxidation state, so bigger ∆oct
All Ni(IV) complexes are low spin because of this
What’s significant about Pd and Pt?
They’re both very rare metals
How do Pd and Pt occur in nature?
Tend to concentrate in sulfides and arsenides - soft Lewis acids
How are Pd and Pt extracted from impure ores?
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
How is Pd/Pt recovered from the ‘anode sludge’ in extraction?
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]
What’re the uses of palladium?
Used as catalyst for syntheitic chemistry, C-C bond-forming.
- also as cat. Converter in cars
Jewellery & dentistry
What’re the uses of platinum?
Jewellery & dentistry
Catalysts - cat. Converters w Rh
- nitric acid synthesis
- fuel cell catalyst
Crucibles for high temp chemical processing
What properties do Pd/Pt(II) always have?
They’re d8 so ALWAYS square planar, diamagnetic - even with weak field ligands
What complex is an exception to platinum group metals geometry?
PdF2 - which is octahedral and has 2 unpaired e- per Pd
Purple
What’re the most important ligands within Pt group metals complexes?
Organometallic ligands; as they tend to form most stable complexes, due to Pd/Pt being ‘softer’ then Ni
What is the rate of Pt(II) ligand substitution?
Slow - ‘inert’ to ligand substitution - ideal rate
Not as slow as Os
What’s the difference between Ni(III) and M(III)?
Ni(III) are low spin d7 6-coordinate, fairly common
Pd(III) and Pt(III) are VERY rare
How is ‘Wolfram’s red salt’ made?
Treat rate yellow [Pt(EtNH2)]2+ in water with Cl2
Deep red PtCl3.4EtNH2 is produced
What’s the structure of ‘Wolfram’s red salt’?
Chain of alternating square planar Pt(II) and octahedral trans-Pt(IV)
Cl- ions H-bond to EtNH2 groups
What common trend do 4d/5d metals show?
That they prefer even-number d^n configurations with no unpaired electrons
What oxidation state is common for Pt but not for Pd?
Pt(IV) is common but Pd(IV) requires anionic ligands - [PdF6]2- is only known complex, Pt has many
What MX4 halide complexes are known?
All PtX4 complexes are known
But only PdF6, [PdI6]2- has been made but never isolated
What does Pd(V) require to be stable?
Needs either anionic ligands or very strong donors like Me-.
Complex needs to be either anionic or neutral
What’s the problem with cat ionic Pd(IV) complexes?
They are easily reduced to Pd(II).
How do Pt(IV) complexes compare to Pd(IV) complexes?
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-)
How are P(IV) complexes usually made?
By either oxidation of Pt(II) complexes or substitution of [PtCl6]2-
What aren’t there any oxidation states past 4+ for palladium?
Already high oxidation state, d6 low-spin which is VERY hard to disrupt filled t2g set.
What does high temperature and high pressure fluoridation of PtCl2 result in?
Gives [PtF6]-
One of the strongest oxidising agents known
