The Student Room Group
Are you sure your not getting confused between the formula for tet and oct as the orbital sets are reversed for them?

For oct it should be (0.4x-0.6y)∆oct so a d5 => low spin = 5x0.4∆oct= 2∆oct and high spin = 3x0.4∆oct-2x0.6∆oct = 0∆oct

But I've been wrong a lot lately :p:
Yeah but look here: http://chemistry.hull.ac.uk/lectures/sja/06513%20SJA%20handout2%20notes.pdf

Ok so the formula is as follows:

Octahedral: (0.4x-0.6y)∆oct
Tetrahedral: (-0.4x+0.6y)∆oct

Also, is there a difference between the terms LFSE (Ligand Field S. E.) and CFSE (Crystal Field S. E.)?
Reply 3
Is the problem just the sign, then? It doesn't really matter which sign you use, I don't think. That it is a stabilisation (so technically a negative quantity) is implied in the very name, so I always quote it without a minus sign. But either way works, it's up to you how you want to do it. :smile:

As for LFSE vs CFSE - they're similar terms, although not strictly speaking the same. CFSE is derived using a purely electrostatic approach (crystal field theory), whilst LFSE is based on MO-theory, i.e. covalency is included. Technically t2g and eg orbitals come from the group theory used in MO theory, but they're also used by analogy in CF-theory. Which term you use depends on whether you use covalent or electrostatic arguments.
Sinuhe
Is the problem just the sign, then? It doesn't really matter which sign you use, I don't think. That it is a stabilisation (so technically a negative quantity) is implied in the very name, so I always quote it without a minus sign. But either way works, it's up to you how you want to do it. :smile:

As for LFSE vs CFSE - they're similar terms, although not strictly speaking the same. CFSE is derived using a purely electrostatic approach (crystal field theory), whilst LFSE is based on MO-theory, i.e. covalency is included. Technically t2g and eg orbitals come from the group theory used in MO theory, but they're also used by analogy in CF-theory. Which term you use depends on whether you use covalent or electrostatic arguments.


Thanks a bunch!
So for first year undergraduate you would use the term CFSE I guess, seeing that ligand field theory is second year material.
Caperucitaroja
Thanks a bunch!
So for first year undergraduate you would use the term CFSE I guess, seeing that ligand field theory is second year material.


Yeah, I was taught crystal field theory in my first year and ligand field theory in my second year :smile:
EierVonSatan
Yeah, I was taught crystal field theory in my first year and ligand field theory in my second year :smile:


Thanks a lot! Very much appreciated, given that I have to retake inorganic due to my unwillingness to memorise pages of reactions. However I am doing it now otherwise I will be kicked out, and I am not that fervently idealistic to be kicked out because of my principles.
Reply 7
Pages of reactions? For inorganic? Sounds more like organic to me. Inorganic is all about waffling on a load of pointless crap about Zeff increasing or decreasing, and penetration and shielding, and counting electrons! Oh, and bluffing your way through route map questions.
One last question,
can I use the Jahn-Teller theorem to account for the rutile (TiO2) solid-state structure? Because that's labelled as a "distorted" lattice.
Reply 9
No - because it's d0 - so the distortion isn't due to the Jahn-Teller effect.
cpchem
No - because it's d0 - so the distortion isn't due to the Jahn-Teller effect.


Ah, :p:
True. Thanks!
Caperucitaroja
My book (Shriver Atkins) gives it as (0.4x-0.6y)∆oct for an octahedral complex with electron configuration (t2g)x(eg)y
However, everywhere else it seems like the formula is (-0.4x+0.6y)∆oct

Any thoughts on what the accepted equation is?


Sorry for digging up an old thread, but the older edition of Atkins (3rd) lists the formula as -0.4x... However, the LFSE as given in the tables are given as positive in spite of it, so I guess the newer edition swapped the signs?