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CHEM0902/C06K
INORGANIC CHEMISTRY
First row transition metals
Catalysts and coloured compounds(continued)
Ainka Brown
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Transition metals
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Electronicconfiguration
Catalytic ability Colouredcompoundsand complexes
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Orbital shapes and energies
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1
2 3 4
nucleus
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Orbital shapes and energies
• Filling electrons:
- minimise energy
- minimise repulsion
- when a shell is filled with electrons it raises
energy of shell above (HOW???)
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What is meant by a low energy shell?
Assumption:
Sub-orbitals have same energy in all elements.
Generally true, but not always
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Orbital shapes and energies
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Period 4: unexpected electron configurations
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K [Ar] 3d0 4s1
Ca [Ar] 3d0 4s2
Sc [Ar] 3d1 4s2
Ti [Ar] 3d2 4s2
V [Ar] 3d3 4s2
Cr [Ar] 3d5 4s1
Mn [Ar] 3d5 4s2
Fe [Ar] 3d6 4s2
Co [Ar] 3d7 4s2
Ni [Ar] 3d8 4s2
Cu [Ar] 3d10 4s1
Zn [Ar] 3d10
4s2
*
*
4s orbitals have a
slightly lower energy
than 3d orbitals)
1s
2s
2p
3s3p4s3d
4p
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Unexpected electron configurations
Predicted
Actual
2 out of 3 e-
are in lower Esub-orbital
Lower E outweighs
electronic replusion
All the e- are in higher E
sub-orbital
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RE
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Unexpected electron configurations
Similar trend for Ti and V
Predicted Actual
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ER
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Unexpected electron configurations
Predicted Actual
1 of the e- is in lower E sub-
orbital plus no repulsion
All e- are in higher E sub-orbital,
plus repulsion
OR
Four of the e- are in higher E sub-
orbital, plus repulsion
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ER
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Unexpected electron configurations
Predicted Actual
2 of the e- are in lower E sub-
orbital plus less repulsion
All e- are in higher E sub-orbital,
plus repulsion
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Similar trend for Fe and Co
ER
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Unexpected electron configurations
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Predicted Actual
OR
All e- are in higher E sub-orbital,plus repulsion
2 of the e- is in lower E sub-orbital plus less repulsion
Lower energy arrangement
In both there is repulsion
and a half-filled orbital
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Remembering configurations
• (Exceptions Cr and Cu)
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4s
3d
Think “2 10”
What is configuration of Co3+ ?
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Characteristics of transition metals
• Criteria:
variable oxidation state
ions with partially-filled d-orbitals
catalytic activity
formation of complex ions
coloured complexes/compounds
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Oxidation states of transition metals
• Lose 4s electrons first (shielding by 3d)
• Can lose/share both 3d and 4s
• Readiness to be oxidised decreases left to right
(correlation with I.E and Zeff )
•
Oxidation potentials show will readily form +2 and +3cations in H+
(Except Cu. Needs something stronger)
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Oxidation potentials
Eθ /V Oxidation ½ eqn. Eθ /V Oxidation ½ eqn. 0.45 Fe(s) → Fe2+ + 2é 2.08 Sc(s) Sc3+ + 3é 0.28 Co(s) → Co2+ + 2é 1.63 Ti(s) Ti2+ + 2é 0.26 Ni(s) → Ni2+ + 2é 1.18 V(s) V2+ + 2é
-0.34 Cu(s) → Cu2+
+ 2é 0.91 Cr(s) Cr2+
+ 2é 0.76 Zn(s) → Zn2+ + 2é 1.18 Mn(s) Mn2+ + 2é
H2(g) → H+ + 2é Eθ = 0.00 V 15
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Oxidation states of transition metals
• High oxidation state = good oxidizing agents,
(e.g. Cr2O72-
, MnO4-)
• Low oxidation state in early part of series = goodreducing agent
(e.g. V2+, Cr2+)
• Later in series poor reducing agent (high Zeff )
• (e.g.Co2+, Ni2+, Cu2+ and Zn2+)
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Catalytic activity
• A catalyst is a substance which speeds up a reaction, butis chemically unchanged at the end of the reaction
• Characteristics:
ability to change oxidation state.
ability to adsorb substances unto their surface(helps to activate them)
• Two types:
heterogenous
homogenous
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HOW ?
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Heterogenous vs. homogenous
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Heterogenous Homogenous
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Some heterogenous catalysts
Catalysts Reaction MnO2 Decomposition of H2O2 V2O5 Contact Process
Fe Haber Process Pt/Rh Ostwald Process
Ni/Pd/Pt Hydrogenation
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Heterogenous catalysts
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Heterogenous catalysts
Reading Assignment!!!!!!
How does V2
O5
catalyse the Contact Process?
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Homogenous Catalysis
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Peroxodisulfate + Iodide
What are the
changes in oxidation
state?
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Formation of complex ions
• Trasition Metal ions can undergo dative covalentbonding
(Empty 3d, 4s, 4p and 4d orbitals can accommodate)
• Examples in nature
(hemoglobin, vitamin B12)
• Do not need to know how bonding
occurs in depth
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Bonding in Complex ions
• Ligands – molecule or ions surrounding metal ion
(have lone pair or negative charge)
e.g. H2O, Cl-, NH3 etc.
• Donor atom – atom that does the actual bonding
• Coordination number – number of donor atoms aroundthe metal ion
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Bonding in Complex ions
25Taken from: www.chemguide.co.uk
Note charge on
metal is not
quenched!!!
Just re-distributed!!
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Coloured ions/compounds
• In complexes d-orbitals have different energies
• Ligands cause electron-electron repulsions
• d-orbital splitting occurs
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∆ E ∆ E
Which +2
transition metal
cation does this
represent ?OR
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Coloured ions/compounds
• Can have d→ d transitions
• (absorb visible light)
• Colour is dependent on ∆ E
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∆ E
600 nm
560 nm
490 nm430
400 nm
800 nm
650 nm
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Coloured ions/compounds
• ∆ E is affected by:
- oxidation state of ion
- ligands
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CuSO4 Co(NO3)2
K2Cr2O7
K2CrO4
NiCl2
KMnO4
∆ E
There are
anomalies.
Colour not
due to
d→d
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Coordination Chemistry
The colours of Chemistry and the
Chemistry of colours
Ainka Brown
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Transition metal complexes
• Also known as coordination compounds
• Used as catalysts, medicines and pigments
• Objectives
applying the IUPAC rules for naming
determining and drawing isomers
geometric (cis, trans)
optical
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Transition metal complexes
• May be neutral compounds, cations or anions
(Depends on the ligand)
• Terms to know:
- ligand
- donor atom
- coordination number
- chelate
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Ligand Name Name Molecule Ammine Ammonia :NH3
Aqua Water H2O: Carbonyl Carbon monoxide :CO Nitrosyl Nitrogen oxide :NO
Phosphine Phosphine :PH3 ethylenediamine ethylenediamine en
Neutral ligands
What is the
structure of en? 32
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Anionic ligands
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Ligand Name Name Ion Chloro Chloride Cl- bromo bromide Br- Fluoro Fluoride F- Cyano Cyanide -CN
Hydroxo Hydroxide -OH Nitro Nitrite NO2
- Carbonato Carbonate CO3-
Oxalato Oxalate C2O42-
Oxo Oxide O2-
What is the structure of oxalate?
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Nomenclature
• Please read the relevant section in McMurray
and Fay!!!!!
• We will discuss briefly
•
Practice, practice and practice some more
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Nomenclature
•For salts name cation before the anion, with a spacebetween the names.
• Ligands are named in alphabetical order (prefixes
ignored)
Use di-, tri-, tetra-, etc if more than one monodentate
ligand.
For chelates use bis-, tris- etc. if more than one
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6 ammonias? 2 waters and 4 chlorides ?
2 oxalates and 2 waters? 2 oxalates and 2 chlorides?
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Nomenclature
• No space between ligand names, no space betweenlast ligand and metal
•
Roman numerals in brackets to show oxidation stateof metal
• If metal is part of anionic complex it has a “metallate
name”
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“Metallate names”
Metal Anion name
Titanium titanate
Vanadium vanadate
Chromium chromateManganese manganate
Iron ferrate
Cobalt cobaltate
Nickel nickelate
Copper cuprate
Zinc zincate
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Nomenclature
[Co(NH3)6]Cl3
[Fe(C2O4)3]3-
[Cu(NH3)4]SO4
Na[Cr(OH)4]
Hexaamminecobalt(III) chloride
Trisoxalatoferrate(III) ion
Tetraamminecopper(II) sulfate
Sodium tetrahydroxochromate(III)
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