Cr(II) or Cr2+
Cr [Ar] 4s13d5
Cr2+ [Ar] 3d4
Consider the octahedral complex Cr[(en)3]2+
Cr(II) or Cr2+
Octahedral complex with 4 d electrons
Octahedral complex with 4 d electrons Δ is large
Pairing energy
Δ is small
Δ is large
Typically, lower energy attained by pairing e- before populating higher E.
Cr[(en)3]2+
Octahedral complex with 4 d electrons
Low Spin
High Spin
Crystal field splitting can result in high spin or low spin complexes, depending on the ligands
Which one?
1
Crystal Field Splitting Energy Spectrochemical Series dz2
dx2- y2 Strong Field Large Δ
Δ
Nature of the ligand determines Δ
Ligands arranged in order of decreasing magnitude of the splitting of energies of d orbitals in coordination compounds
dxy
dxz
dyz
Weak Field Small Δ
Strong-field ligands produce a Large Crystal Field Splitting, resulting in Low Spin complexes
Spectrochemical Series Strong Field Large Δ
Δ is Large Weak Field Small Δ
2 unpaired electrons
Weak-field ligands produce a Small Crystal Field splitting, resulting in High Spin complexes
Cr[(en)3]2+
Spectrochemical Series Strong Field
Δ is Small Weak Field
4 unpaired electrons
en is a Strong Field ligand
2
Strong-field ligands produce a large crystal field splitting, resulting in low spin complexes Cr(en)32+
Low Spin
Distinction between high-spin and low-spin octahedral complexes can only be made for d4 to d7 Electron Configurations
d0-d3 and d8-d10 configurations have only one way of filling in e-.
2 unpaired electrons
d0-d3 configurations have only one way of filling in electrons
Distinction between high-spin and low-spin octahedral complexes can only be made for d4 to d7 Electron Configurations
d3
d7
High spin ΔP
How many unpaired electrons does [Re(H2O)6]Cl2 have?
d9 Is it a Low Spin or High Spin Complex?
3
Coordination Compounds How many unpaired electrons does [Re(H2O)6]Cl2 have?
Determine the Shape Determine Oxidation State of the metal Determine Number of of d electrons
[Re(H2O)6]Cl2
Determine if Ligand is Weak field or Strong field
Octahedral Complex
Draw energy level diagram
Re [Xe] 6s25d5
Re2+ [Xe] 5d5
How many unpaired electrons does [Re(H2O)6]Cl2 have?
[Re(H2O)6]2+ 2ClOxidation State? Oxidation State = 2 – (6 x 0) = 2+ Re2+ or Rhenium(II)
How many unpaired electrons does [Re(H2O)6]Cl2 have?
[Re(H2O)6]2+ 2ClE
dz2
dx2-y2
dxy dxz
dyz
Spectrochemical Series
d5
d-orbital splitting in an octahedral crystal field
H2O is a weak field ligand
4
How many unpaired electrons does [Re(H2O)6]Cl2 have?
How many unpaired electrons does [Re(H2O)6]Cl2 have?
[Re(H2O)6]2+ 2Cl-
[Re(H2O)6]2+ 2Cl-
dz2 dx2-y2
d5
Δ is small
dxy dxz dyz
d5
dz2 dx2-y2
5 unpaired e-
dxy dxz dyz
Co [Ar] 4s23d7
High-spin complex
Co3+ [Ar] 3d6
MAGNETIC PROPERTIES Why [CoF6]-3 is paramagnetic and [Co(NH3)6]+3 is diamagnetic
Octahedral Co3+
d-orbital splitting in a Weak octahedral crystal field
Spectrochemical Series
Δ is small
Strong Field
Weak Field
F-
is a Weak Field ligand
5
High-Spin complex
Spectrochemical Series Strong Field
Weak Field
NH3 is a Strong Field ligand Paramagnetic
d-orbital splitting in a Strong octahedral crystal field
Low-Spin complex High-Spin complex
High-Spin complex
Δ is Large
Paramagnetic
The effects of ligands on the colors of coordination compounds
[CoCl(NH3)5](NO3)2
Paramagnetic
Diamagnetic
The effects of ligands on the colors of coordination compounds
[CoBr(NH3)5](NO3)2
6
The effects of ligands on the colors of coordination compounds
The effects of ligands on the colors of coordination compounds
[CoI(NH3)5](NO3)2
[CoNO2(NH3)5](NO3)2
The effects of ligands on the colors of coordination compounds
The effects of ligands on the colors of coordination compounds
[CoSO4(NH3)5]NO3
[CoCO3(NH3)5]NO3
Visible Spectrum (Each wavelength corresponds to a different color)
400 nm Higher energy Shorter Wavelength 400 nm
500 nm
600 nm
700 nm Lower energy Longer Wavelength
700 nm
Eye can detect photons from 400-700nm
White = all the colors (wavelengths)
7
Blue Magenta
Cyan
Yellow
Green
Red
Blue
"White" light
Magenta Cyan Yellow
Green
Red
Blue Blue Cyan
Red Yellow
Yellow Green
8
Blue Blue Magenta
Red
Green Green
Red
Green
Blue Blue
Green
Red Green Red
Light
Compound
Coordination compounds are highly colored because they can absorb photons in the visible region of the electromagnetic spectrum to produce the complementary color.
Eye
9
A solution of [CuCl4]-2 is yellow. In what region of the electromagnetic spectrum does it absorb light?
Blue
Yellow 500 nm
400 nm
600 nm
700 nm
A solution of [Cu(H2O)4]+2 absorbs mostly at 580 nm. What should be its color? [CuCl4]-2
500 nm
400 nm
Blue
600 nm
700 nm
Blue
Green
Red
Yellow Green
Red
10
[Cu(H2O)4]+2
Explain the colors of:
Coordination compounds are highly colored because they can absorb photons in the visible region of the electromagnetic spectrum to produce the complementary color.
Cr [Ar] 4s13d5
Cr3+ [Ar] 3d3
[Cr(NH3)6]Cl3 and [Cr(H2O)6]Cl3
Oxidation State: Cr3+
[Cr(NH3)6]Cl3
Spectrochemical Series dz 2
dx2-y2
Δ Large
NH3 is a stronger field ligand
dxy
dxz
dyz
11
[Cr(NH3)6]Cl3 absorbs at higher frequency (lower wavelength) i.e. in the blue.
500 nm
400 nm
600 nm
700 nm
[Cr(NH3)6]Cl3 absorbs at higher frequency (lower wavelength) i.e. in the blue. The complementary color is yellow
400 nm
500 nm
600 nm
700 nm
[Cr(H2O)6]Cl3
Spectrochemical Series dz 2
dxy
H2O is a weaker field ligand
[Cr(H2O)6]Cl3 absorbs at lower frequency (higher wavelength) i.e. in the yellow.
400 nm
500 nm
600 nm
700 nm
dx2-y2
dxz
Δ Small
dyz
[Cr(H2O)6]Cl3 absorbs at lower frequency (higher wavelength) i.e. in the yellow. The complementary color is violet.
400 nm
500 nm
600 nm
700 nm
12
Cr2+ [Ar] 3d4
Consider the octahedral complex Cr[(en)3]2+
Cr(II) or Cr2+
Octahedral complex with 4 d electrons
Octahedral complex with 4 d electrons Δ is large
Pairing energy
Δ is small
Δ is large
Typically, lower energy attained by pairing e- before populating higher E.
Cr[(en)3]2+
Octahedral complex with 4 d electrons
Low Spin
High Spin
Crystal field splitting can result in high spin or low spin complexes, depending on the ligands
Which one?
1
Crystal Field Splitting Energy Spectrochemical Series dz2
dx2- y2 Strong Field Large Δ
Δ
Nature of the ligand determines Δ
Ligands arranged in order of decreasing magnitude of the splitting of energies of d orbitals in coordination compounds
dxy
dxz
dyz
Weak Field Small Δ
Strong-field ligands produce a Large Crystal Field Splitting, resulting in Low Spin complexes
Spectrochemical Series Strong Field Large Δ
Δ is Large Weak Field Small Δ
2 unpaired electrons
Weak-field ligands produce a Small Crystal Field splitting, resulting in High Spin complexes
Cr[(en)3]2+
Spectrochemical Series Strong Field
Δ is Small Weak Field
4 unpaired electrons
en is a Strong Field ligand
2
Strong-field ligands produce a large crystal field splitting, resulting in low spin complexes Cr(en)32+
Low Spin
Distinction between high-spin and low-spin octahedral complexes can only be made for d4 to d7 Electron Configurations
d0-d3 and d8-d10 configurations have only one way of filling in e-.
2 unpaired electrons
d0-d3 configurations have only one way of filling in electrons
Distinction between high-spin and low-spin octahedral complexes can only be made for d4 to d7 Electron Configurations
d3
d7
High spin ΔP
How many unpaired electrons does [Re(H2O)6]Cl2 have?
d9 Is it a Low Spin or High Spin Complex?
3
Coordination Compounds How many unpaired electrons does [Re(H2O)6]Cl2 have?
Determine the Shape Determine Oxidation State of the metal Determine Number of of d electrons
[Re(H2O)6]Cl2
Determine if Ligand is Weak field or Strong field
Octahedral Complex
Draw energy level diagram
Re [Xe] 6s25d5
Re2+ [Xe] 5d5
How many unpaired electrons does [Re(H2O)6]Cl2 have?
[Re(H2O)6]2+ 2ClOxidation State? Oxidation State = 2 – (6 x 0) = 2+ Re2+ or Rhenium(II)
How many unpaired electrons does [Re(H2O)6]Cl2 have?
[Re(H2O)6]2+ 2ClE
dz2
dx2-y2
dxy dxz
dyz
Spectrochemical Series
d5
d-orbital splitting in an octahedral crystal field
H2O is a weak field ligand
4
How many unpaired electrons does [Re(H2O)6]Cl2 have?
How many unpaired electrons does [Re(H2O)6]Cl2 have?
[Re(H2O)6]2+ 2Cl-
[Re(H2O)6]2+ 2Cl-
dz2 dx2-y2
d5
Δ is small
dxy dxz dyz
d5
dz2 dx2-y2
5 unpaired e-
dxy dxz dyz
Co [Ar] 4s23d7
High-spin complex
Co3+ [Ar] 3d6
MAGNETIC PROPERTIES Why [CoF6]-3 is paramagnetic and [Co(NH3)6]+3 is diamagnetic
Octahedral Co3+
d-orbital splitting in a Weak octahedral crystal field
Spectrochemical Series
Δ is small
Strong Field
Weak Field
F-
is a Weak Field ligand
5
High-Spin complex
Spectrochemical Series Strong Field
Weak Field
NH3 is a Strong Field ligand Paramagnetic
d-orbital splitting in a Strong octahedral crystal field
Low-Spin complex High-Spin complex
High-Spin complex
Δ is Large
Paramagnetic
The effects of ligands on the colors of coordination compounds
[CoCl(NH3)5](NO3)2
Paramagnetic
Diamagnetic
The effects of ligands on the colors of coordination compounds
[CoBr(NH3)5](NO3)2
6
The effects of ligands on the colors of coordination compounds
The effects of ligands on the colors of coordination compounds
[CoI(NH3)5](NO3)2
[CoNO2(NH3)5](NO3)2
The effects of ligands on the colors of coordination compounds
The effects of ligands on the colors of coordination compounds
[CoSO4(NH3)5]NO3
[CoCO3(NH3)5]NO3
Visible Spectrum (Each wavelength corresponds to a different color)
400 nm Higher energy Shorter Wavelength 400 nm
500 nm
600 nm
700 nm Lower energy Longer Wavelength
700 nm
Eye can detect photons from 400-700nm
White = all the colors (wavelengths)
7
Blue Magenta
Cyan
Yellow
Green
Red
Blue
"White" light
Magenta Cyan Yellow
Green
Red
Blue Blue Cyan
Red Yellow
Yellow Green
8
Blue Blue Magenta
Red
Green Green
Red
Green
Blue Blue
Green
Red Green Red
Light
Compound
Coordination compounds are highly colored because they can absorb photons in the visible region of the electromagnetic spectrum to produce the complementary color.
Eye
9
A solution of [CuCl4]-2 is yellow. In what region of the electromagnetic spectrum does it absorb light?
Blue
Yellow 500 nm
400 nm
600 nm
700 nm
A solution of [Cu(H2O)4]+2 absorbs mostly at 580 nm. What should be its color? [CuCl4]-2
500 nm
400 nm
Blue
600 nm
700 nm
Blue
Green
Red
Yellow Green
Red
10
[Cu(H2O)4]+2
Explain the colors of:
Coordination compounds are highly colored because they can absorb photons in the visible region of the electromagnetic spectrum to produce the complementary color.
Cr [Ar] 4s13d5
Cr3+ [Ar] 3d3
[Cr(NH3)6]Cl3 and [Cr(H2O)6]Cl3
Oxidation State: Cr3+
[Cr(NH3)6]Cl3
Spectrochemical Series dz 2
dx2-y2
Δ Large
NH3 is a stronger field ligand
dxy
dxz
dyz
11
[Cr(NH3)6]Cl3 absorbs at higher frequency (lower wavelength) i.e. in the blue.
500 nm
400 nm
600 nm
700 nm
[Cr(NH3)6]Cl3 absorbs at higher frequency (lower wavelength) i.e. in the blue. The complementary color is yellow
400 nm
500 nm
600 nm
700 nm
[Cr(H2O)6]Cl3
Spectrochemical Series dz 2
dxy
H2O is a weaker field ligand
[Cr(H2O)6]Cl3 absorbs at lower frequency (higher wavelength) i.e. in the yellow.
400 nm
500 nm
600 nm
700 nm
dx2-y2
dxz
Δ Small
dyz
[Cr(H2O)6]Cl3 absorbs at lower frequency (higher wavelength) i.e. in the yellow. The complementary color is violet.
400 nm
500 nm
600 nm
700 nm
12
