crystal field theory Flashcards
does crystal field theory assume that bonding in TM complexes are ionic or covalent?
ionic (no covalent character)
electrostatic interactions (point charge interactions between the metal and the ligand)
which d orbitals lie on the axis and which ones lie inbetween for octahedral
on: dx^2-y^2 and dz^2
between: dxy, dxz, dyz
what is the natural state of the d orbitals in free metal ions?
all 5 d orbitals are degenerate
what happens to degenerate orbitals when placed in a ligand field?
the ligands are negatively charged or have lone pairs of electrons which repel the electrons found in the d orbitals therefore energy of the d orbitals increase BUT this assumes a negative charge field
-> change of POV by assuming ligands as negative point charges
how are the d orbitals distributed in an octahedral ligand?
dx^2-y^2 and dz^2 directly interact with the concentrated negative point charge of the ligands (repulsion) thus become destabilized and go higher in energy
dxy, dxz, dyz are between the axis thus are electronically relived as they do not point directly towards the ligand (stabilized and energy is lowered)
- these are relative to if the ligands created a sphere of negative charge where all orbitals experience the same amount of repulsion
what are the higher energy and lower energy orbitals called in octahedral complexes?
higher: eg (equal)
lower t2g (triplet)
what is the barycenter
energy of a spherical ligand field, energy is raised or lowered relative to this value
what is CFSE? what represents a more stable value
the stabilisation of the particular arrangement of ligands in a specific geometry with respect to the spherical ligand field
the more negative the value the more stable the complex
what is the general CFSE equation for oct and tet?
CFSE(oct) = (-2/5 x no. of electrons in t2g + 3/5 x no. of electrons in eg) x doct + zP
CFSE(tet) = (-3/5 x no. of electrons in t2 + 2/5 x no. of electrons in e) x dtet + zP
zP is the number of extra paired electrons COMPARED TO the barycenter form
what is the CFSE of a barycenter geometry of any metal complex?
0
what is high spin and low spin
high spin: more unpaired electrons (promoted to HIGHER energy level)
-> all electrons pointing in the same direction therefore higher net spin
low spin: less unpaired electrons (electrons are paired up in lower energy orbital)
-> not all electrons spinning in the same direction therefore lower net spin
what determines the size of P
metal + oxidation state
what determines the size of doct
metal, oxidation state, ligand
what is the range of d values that have high/low spin state for octahedral?
d4-d7
which 2 states have no net benefit compared to barycentre?
high spin of d5 and d10