Unit 3: Coordination Chemistry Flashcards
What are the similar properties of transition metals?
- Relatively high electrical conductivity
- Relatively high thermal conductivity
- More than 1 oxidation state
- Often form complex ions
- Most can absorb visible light
- Many compounds are paramagnetic
What are the different properties of transition metals?
- Melting points
- Hardness
- Oxides
What groups follow the stability rule in regard to electron configuration?
Group 6 and group 11
What makes up a coordination compound?
It is made of a complex ion and counter ions.
What is coordination numbers?
The number of bonds from the ligands to the central metal atom.
What are counter ions?
Ions which are needed to maintain charge neutrality of the compound.
What shape forms from a coordination # = 2?
Linear, is the least common shape.
What shape forms from a coordination # = 4?
Square planar or tetrahedral
What shape forms from a coordination # = 6?
Octahedral, most common
How can you determine whether a CN of 4 will be square planar or tetrahedral?
If the electron configuration of the metal is nd8 the shape will most likely be square planar.
For all other metals, it will be tetrahedral.
What is a ligand?
It is a neutral molecule or an ion with a lone pair of e-‘s
What is a monodenate/unidentate ligand?
It is attached to the metal by one bond.
fluoro
F-
chloro
Cl-
bromo
Br-
iodo
I-
cyano
CN-
hydroxo
OH-
aqua
H20
ammine
NH3
carbonyl
CO
nitrosyl
NO
Polydentate lignads?
Attached to metal by more than 1 bond or pair of electrons.
Bidentate?
2 pairs e-
ethylenediamine
en
oxalate
ox2-
How do you name a complex ion?
- Cation named before anion
- Name ligands before metal
- Use prefixes for ligands
- Designate the oxidation # of metal using Roman numerals
What is different about period 4 transition metals?
They are active enough to reduce H+ from acid solution.
What are the two main types of isomers?
Structural isomers and stereoisomers.
What are the two types of structural isomers?
Coordination isomers
- Ligand and counter-ion exchange
Linkage isomers
- Different donor atom
What are the two types of stereoisomers?
Geometric isomers
- Different arrangements around the metal ion
Optical isomers
- non-superimposable mirror images
What are the bond names for SCN-?
via sulfur: thiocyanato
via nitrogen: isothiocyanato
What are the bond names for OCN-?
via oxygen: cyanato
via nitrogen: isocyanato
What are the bond names for NO2-?
via nitogen: nitro
via oxygen: nitrito
What is a cis geometric isomer?
Identical ligands are 90* apart.
What is a trans geometric isomer?
Identical ligands are 180* apart
What is a facial geometric isomer?
All 3 identical ligands are 90* apart
What is a meridional geometric isomer?
2 identical ligands are 180* apart and 1 identical ligand is 90* apart from the other 2.
What is the crystal field theory?
It is a bonding model which explains the properties of transition metals.
What is the eg set?
dz2, dx2-y2
The orbital energy goes up (destabilized)
The ligand lone pair is aligned with the orbital
What is the t2g set?
dxy, dxz, dyz
The orbital energy goes down (stabilized)
The ligand lone pair is between orbitals
What is a free ion?
d-orbitals have same energy (degenerate)
Crystal field splitting?
Energy splitting, explains the magnetic properties of transition metals.
What happens if the crystal field splitting is small?
- Pairing is not favorable
- e- will fill t2g and eg sets before pairing
- Forms high-spin complexes
- High # of unpaired e-
What happens if the crystal field splitting is large?
- Pairing is favorable
- e- will fill t2g set first then eg set
- Forms low-spin complexes
- Low # of unpaired e-
Does the magnitude of the crystal-splitting energy increase with the more valance e-?
Yes
What is a diamagnetic species?
Not attracted to a magnetic field and all electrons are paired.
What is a paramagnetic species?
Attracted to a magnetic field and has unpaired electrons.
Why do we observe colours in transition metals?
The splitting of energy splits the d-orbital into 2 levels, which causes energy to be absorbed.
We see the colour is the opposite of the wavelength absorbed.
