Crystal field stabilization energy

Crystal field stabilization energy

1. Crystal field stabilization energy

2. Contents Crystal Field Stabilization Energy Calculation Factors

3. CFSE: When the ligand approach central metal atom there is repulsion between the ligand electrons and the d orbital electrons of central metal atom. The ligand approach the central metal atom along the axis or between the axis. When a ligand approach a central metal atom the d-orbital splits into two sets and The gap between the and is called energy gap or crystal field stabilization energy.  

4. Crystal Field Stabilization energy for different complexes Crystal Field Stabilization energy for different complexes are following Octahedral complexes  Tetrahedral complexes

5. Crystal field stabilization energy for octahedral complex The energy difference between and sets called is proportional to the crystal field strength of ligands ,that how strongly the ligand electrons repel the metal electrons. Energy is high in the axis - and and energy is low in the xy,yz and zx  

6. Energy Of Orbitals: The energy of each of the two high- energy orbitals  is increased by  above their energy in a spherical field , while the energy  of each of the three low energy orbital  is decreased by   below their energy in a spherical field . The total increase is equal to the total decrease, so                      (2)[ ]=(3)[ ] The  d-electrons  on the metal ion occupy the   set in preference to the higher ,energy  set .  

7. The   orbitals are called non bonding orbitals in octahedral complexes , but the  orbitals are called anti bonding orbitals because that are forced to occupy these orbitals are quite strongly repelled by the relatively close approach of ligand electrons, and tend to destabilize the octahedral complex  

8. Calculation of crystal field stabilization Calculation of crystal field stabilization energy for octahedral complexes from dᶦ to dᶦ° energy system Calculation of crystal field stabilization energy for octahedral complexes from dᶦ to dᶦ° energy system

9. The electron arrangement and CFSE for octahedral complexes Configuration Strong Field (low spin) CFSE Weak Field (high spin) CFSE dᶦ t₂gᶦ eg° -0.4Δₒ t₂gᶦ eg° -0.4Δₒ d² t₂g² eg° - 0.8Δₒ t₂g² eg° -0.8Δₒ d³ t₂g³ eg° - 1.2Δₒ t₂g³ eg° -1.2Δₒ d⁴ t₂g⁴ eg° -1.6Δₒ t₂g³ egᶦ -0.6Δₒ d⁵ t₂g⁵ eg° -2.0Δₒ t₂g³ eg² 0 Δₒ d⁶ t₂g⁶ eg° -2.4Δₒ t₂g⁴ eg² -0.4Δₒ d⁷ t₂g⁶ egᶦ -1.8Δₒ t₂g⁵ eg² -0.8Δₒ d⁸ t₂g⁶ eg² -1.2Δₒ t₂g⁶ eg² -1.2Δₒ dꝰ t₂g⁶ eg³ -0.6Δₒ t₂g⁶ eg³ -0.6Δₒ dᶦ° t₂g⁶ eg⁴ 0 Δₒ t₂g⁶ eg⁴ 0 Δₒ

10. Crystal field stabilization energy for tetrahedral complex The energy difference between and sets called is proportional to the crystal field strength of ligands ,that how strongly the ligand electrons repel the metal electrons. Energy is low in the axis - and and energy is high in the xy,yz and zx  

11. Energy of orbitals The energy of each of the two low- energy orbitals  is decreased by  above their energy in a spherical field , while the energy  of each of the three high energy orbital  is increased by   below their energy in a spherical field .  

12. Calculation of crystal field stabilization energy for tetrahedral complexes

13. # of d-electrons Tetrahedral CFSE # of d-electron Tetrahedral CFSE 1 -6Δq 6 -6Δq 2 -12Δq 7 -12Δq 3 -8Δq 8 -8Δq 4 -4Δq 9 -4Δq 5 0Δq 10 0Δq

14. Factors affecting crystal field stabilization   Factors affecting crystal field stabilization energy are following Nature of ligand Nature of metal cation Quantum number Geometry of complexes

15. Nature of ligand If weak ligands approach metal, less splitting of d-orbital occurs and energy gap (crystal field stabilization energy) would be small. If strong ligand approach metal, more splitting of d-orbital occurs and energy gap (crystal field stabilization energy) would be large  Geometry of complexes Order of crystal field stabilization energy according to geometry of complexes is Δsp (square planner) > Δo (octahedral) > Δt (tetrahedral) 1.73 > 1.23 > 0.43

16. Nature of metal cation If different charges on cation are present of same metal then high charged will polarize the ligand more effectively. For example: Fe²ᶧ[(H₂O)₆]²ᶧ Fe³ᶧ[(H₂O)₆]³ᶧ If different charges on cation are present on different metals then metal having high charge will be more easily approached by ligands. For example: [V²ᶧ(H₂O)₆]²ᶧ , [Cr³ᶧ(H₂O)₅]³ᶧ Ligand will easily approach the chromium metal as compared to vanadium.

17. If same charges on cations are present but there is difference in number of d-orbitals then metal having less number of electrons would have high energy gap (crystal field stabilization energy) . For example: [Co(H₂O)₆]²ᶧ [Ni(H₂O)₅]²ᶧ Here Ni has less value of CFSE as it has d⁸ system and Co has d⁷ system

18. Quantum number If quantum number of central metal ion is high then energy gap (crystal field stabilization energy) would be large Order of increase in CFSE according to quantum number is 3d< 4d<5d