Open main menu
Home
Random
Recent changes
Special pages
Community portal
Preferences
About Wikipedia
Disclaimers
Incubator escapee wiki
Search
User menu
Talk
Dark mode
Contributions
Create account
Log in
Editing
Ligand field theory
(section)
Warning:
You are not logged in. Your IP address will be publicly visible if you make any edits. If you
log in
or
create an account
, your edits will be attributed to your username, along with other benefits.
Anti-spam check. Do
not
fill this in!
==High and low spin and the spectrochemical series== {{main|Spin states (d electrons)}} {{see also|Magnetochemistry}} {{Unreferenced section|date=January 2021}} The six bonding molecular orbitals that are formed are "filled" with the electrons from the ligands, and electrons from the ''d''-orbitals of the metal ion occupy the non-bonding and, in some cases, anti-bonding MOs. The [[energy]] difference between the latter two types of MOs is called Ξ<sub>O</sub> (O stands for octahedral) and is determined by the nature of the Ο-interaction between the ligand orbitals with the ''d''-orbitals on the central atom. As described above, Ο-donor ligands lead to a small Ξ<sub>O</sub> and are called weak- or low-field ligands, whereas Ο-acceptor ligands lead to a large value of Ξ<sub>O</sub> and are called strong- or high-field ligands. Ligands that are neither Ο-donor nor Ο-acceptor give a value of Ξ<sub>O</sub> somewhere in-between. The size of Ξ<sub>O</sub> determines the electronic structure of the ''d''<sup>4</sup> - ''d''<sup>7</sup> ions. In complexes of metals with these ''d''-electron configurations, the non-bonding and anti-bonding molecular orbitals can be filled in two ways: one in which as many electrons as possible are put in the non-bonding orbitals before filling the anti-bonding orbitals, and one in which as many unpaired electrons as possible are put in. The former case is called low-spin, while the latter is called high-spin. A small Ξ<sub>O</sub> can be overcome by the energetic gain from not pairing the electrons, leading to high-spin. When Ξ<sub>O</sub> is large, however, the spin-pairing energy becomes negligible by comparison and a low-spin state arises. The [[spectrochemical series]] is an empirically-derived list of ligands ordered by the size of the splitting Ξ that they produce. It can be seen that the low-field ligands are all Ο-donors (such as I<sup>β</sup>), the high field ligands are Ο-acceptors (such as CN<sup>β</sup> and CO), and ligands such as H<sub>2</sub>O and NH<sub>3</sub>, which are neither, are in the middle. I<sup><nowiki>−</nowiki></sup> < Br<sup><nowiki>−</nowiki></sup> < S<sup>2<nowiki>−</nowiki></sup> < SCN<sup><nowiki>−</nowiki></sup> < Cl<sup><nowiki>−</nowiki></sup> < NO<sub>3</sub><sup><nowiki>−</nowiki></sup> < N<sub>3</sub><sup><nowiki>−</nowiki></sup> < F<sup><nowiki>−</nowiki></sup> < OH<sup><nowiki>−</nowiki></sup> < C<sub>2</sub>O<sub>4</sub><sup>2<nowiki>−</nowiki></sup> < H<sub>2</sub>O < NCS<sup><nowiki>−</nowiki></sup> < CH<sub>3</sub>CN < py ([[pyridine]]) < NH<sub>3</sub> < en ([[ethylenediamine]]) < bipy ([[2,2'-bipyridine]]) < phen (1,10-[[phenanthroline]]) < NO<sub>2</sub><sup><nowiki>−</nowiki></sup> < PPh<sub>3</sub> < CN<sup><nowiki>−</nowiki></sup> < CO
Edit summary
(Briefly describe your changes)
By publishing changes, you agree to the
Terms of Use
, and you irrevocably agree to release your contribution under the
CC BY-SA 4.0 License
and the
GFDL
. You agree that a hyperlink or URL is sufficient attribution under the Creative Commons license.
Cancel
Editing help
(opens in new window)