Transition Metals Flashcards
Define a transition metal as opposed to a d block element
TM: exists with partially filled d-block sub-shell in at least one of its compounds
D block: ground state has outer e- in d sub-shell
Name two characteristics of TM electron configuration
Lose 4s before 3d
Cu/Cr: 4s1 ground state (sub shells very energetically similar)
Which elements are excluded from transition metals
Exclude Sc down
(Include Zn down)
Sc3+ = 4s03d0
Zn2+ = 4s03d10
Name 4 general TM properties
Complex ions
Often coloured compounds
Often catalytic behaviour
Range of oxidation states
How are complex ions formed
Metal accepts e- from ligand lp
Dative cov bonds
Ligand
Donates lp to TM
Coordination number
No. Bonds to lps
1-5 prefixes
Mono
Di
Tri
Tetra
Penta
Hexa
H2O suffix
Aqua
NH3 suffix
Ammine
Cl- suffix
Chloro
OH- suffix
Hydroxy
CN- suffix
Cyano
Naming complex ions order
No. Ligands
Type of ligand
Metal
Oxidation no. Of metal
Name 4 possible complex ion shapes
6 octahedral
2 linear
4 tetrahedral
4 planar
Monodentate ligand
Attach to metal ion via one lp
Polydentate ions
Attach to metal ion with more than one lp
Di/tri/tetra
Usually organic diamines/dioates
Isolated atom subshell arrangement
Equal 5 d sub shells
e-s bound with same NRG
Same diagram NRG level
Complex ion subshell arrangements
Orbitals de/stabilised by ligands
Unequal orbitals
How is colour created by complex ions
e- in bottom group
e- vacancy in top group
Absorbs visible light of a specific frequency
e- excited
Reflects the rest of white light as photons
Describe octahedral vs tetrahedral subshell structure
Octahedral: 2 top, 3 bottom
Tetrahedral: 3 top, 2 bottom
What does the light frequency needed to excite an e- depend on
Orbital groups energy gap
Octahedral (usually) > tetrahedral
Metal oxidation state
Ligand nature
Industrial dyes
Use e- excitation
Gap can be made without d orbital splitting
Why does deprotination occur
Some metal +ve offset by e- ligand donation
Aqua: spread +ve to H
Increase +ve H compared to pure water
More likely H+ dissociation
Acidic behaviour
Especially in 3+ metals
Forced deprotination using a base
Continue until ion has no charge
Insoluble ppte
OH in product is not the added base
Base removes H+ from H2O
Acid strength
Polyprotic weak acids
Weaker with successive deprotinations
Some amphoteric
Uncharged ppte acidic enough to deprotination —> -ve charged
Hexaaquaccopper (II) excess NH3 colour change
Pale blue solution to dark blue solution
Hexaaquaccobalt (II) excess NH3 colour change
Pink solution to brown solution
Hexaaquacchromate (III) excess NH3 colour change
Green solution to purple solution
Hexaaquacchromate (III) excess OH- colour change
Green solution to dark green solution
Hexaaquacchromate (III) limited NH3/OH- colour change
Green solution to grey-green ppte
Hexaaquacferrate (II) limited NH3/OH- colour change
Pale green solution to dark green ppte
(Oxidised to brown Fe3+ when left)
Hexaaquacferrate (III) limited NH3/OH- colour change
Yellow solution to red-brown ppte
Hexaaquaccobalt (II) limited NH3/OH- colour change
Pink solution to blue ppte
Hexaaquaccopper (II) limited NH3/OH- colour change
Light blue solution to blue ppte
What structure/colour do chlorocopper/cobalt ligand exchanges form
Tetrahedral
Charged ligands produce greater colour changes
Copper: light blue to lime green
Cobalt: Pink to dark blue
Ligand exchange equilibrium
Step wise process
Each step is reversible
Each step has an associated k value
New ligand metal bonds > old = exo
More exo, increase k
Entropy multidentate vs monodentate ligands
Replace mutiple mono with fewer multi
More free product particles
+ve Ssys, increase k
Unfavourable exchange with excess = still get some exchange
EDTA
Fully deprotinated
6 lps
Displace 6 monodentate ligands
Very +ve Ssys
Used as a cleaning agent for metal poisoning and soil/river metal pollution
CO ligand exchange in haemaglobin
Strong monodentate ligand
Bind strongly to Fe2+
Detach oxygen
Practically irreversible
Toxic
Haemaglobin structure
4 polypetide chains
4 haem groups
Fe2+ at each centre
Each dative cov bonded to 4 N lps (porphyrin ring)
Each dative cov bonded to one other globin
6th octahedral position binds to oxygen (oxyhaemaglobin) or water (deoxyhaemaglobin)
O2 and H2O easily switch
TM redox reactions
Many oxidation states so many redox reactions
Use electrode potential data to determine spontaneity/acid or alkali conditions
Use ACW method
Vanadium 4 oxidation states and colours
+5, yellow, VO2(+)
+4, blue, VO2+
+3, green, V3+
+2, purple, V2+
Vanadium 3 half equations
V3+ + e- —> V2+
VO2+ + 2H+ + e- —> V3+ + H2O
VO2(+) + 2H+ + e- —> VO2+ + H2O
4 chromium oxidation states and the conditions they’re produced under
+5, Cr2O7-2, acidic, yellow
+5, CrO4-2, alkali from Cr2O7-2 (H2O2 from Cr3+) orange
+3, Cr3+ acidic (H2O2/Zn from Cr2O7-2, O2 from Cr2+)
+2, Cr2+, acidic (anaerobic Zn from Cr3+)
Heterogenous catalysts
Different state/phase to reactants
Continuous processes
No separation
Reactant molecules adsorb to surface
Weakened reactant bonds
Reactant molecules meet/react on surface
Product molecules desorb
Heterogenous catalyst examples (4)
Ni alkene to alkane
Fe ammonia industrial production
Pt/Rh catalytic converters
- 2NO(g) + 2CO(g) —> N2(g) + CO2(g)
V2O5 H2SO4 production
- S(s) + O2(g) —> SO2(g)
- SO2(g) + 1/2O2(g) —> SO3(g)
— SO2(g) + V2O5(s) —> V2O4(s) + SO3(g)
— V2O4(s) + 1/2O2(g) —> V2O5(s)
- SO3(g) + H2O(l) —> H2SO4(aq)
Homogenous catalysts
Same state/phase as reactants
Batch processes
Separate after mixing
TM aq ions = intermediates
Homogenous catalyst examples (2)
Mn2+
- 2MnO4-(aq) + 16H+(aq) + 5C2O42-(aq) —> 2Mn2+(aq) + 8H2O(l) + 10CO2(g)
- Autocatalyst, product of the reaction
- Start slow, speed up
Fe3+
- 2I-(aq) + S2O8-2(aq) —> I2(aq) + 2SO4-2(aq)
- opp charged species react faster than 2 -ve charged species
— I2 + 2e- —> 2I-
— Fe3+ + e- —> Fe2+
— S2O8-2 + 2e- —> 2SO4-2
