d block part B Flashcards
What assumptions are made for crystal feild theory (2)
- Metal centres and ligands represented as point charges.
2. Bonding arises through electrostatic interactions between these charges
Which D orbitals are directly on the axis
dz2
dx2-y2
Which D orbitals are between the axes
dxy
dxz
dyz
Explain which d orbitals are destabilised in an octahedral complex
dx2-y2 & dz2
Orbitals point directly towards ligands on xyz axes. electrons in orbitals and ligands repel each other, E increases
Explain which D orbitals re more stable in an octahedreal complex
dxy, xz, yz
Orbitals point inbetween xyz axes, electrons in orbitals and ligands electronically relieved by not pointing directly towards each other.
what is a crystal field theory
the predicting of the splitting on d-orbitals into two or more sets of orbitals at different energies in complexes.
describe the 2 new energy sets in CFT
Eg - upper energy set with 2 orbitals
t2g - lower energy with 3 orbitals.
what is crystal field stabilisation energy?
CFSE
stabilisation of particular arrangements of ligands with respect to spherical ligand field (barycentre)
What is CFSE equation
[(-2/5 x num electrons in t2g) + (+3/5 x num elecrons in eg)]Delta oct + zP
How are magnetic properties determined?
no unpaired e = diamagnetic
at least 1 unpaired e = paramagnetic.
What are high spin and low spin complex arrangements when do they occur?
High spin: more unpaired electrons, weak field, when DeltaOct is small.
Low spin: Fewer unpaired electrons, strong field, When DeltaOct is large
How to determine High or low spin?
High spin when DeltaOct< pairing energy
Low spin DeltaOct >pairing energy
Whats special about d8, 9 and 10 central metals
High and low spins don’t exist,
d10 and d5 CFSE is 0
How does DeltaOct change with oxidation state?
DeltaOct increases with OS as pulls ligands closer as increased effective nuclear charge, larger electrostatic repulsions between electrons in orbitals and ligands, more d splitting
How Does DeltaOct change down group?
Increases, Larger d orbitals, better contact with ligands, more interactions, more destabilising.
Larger orbitals pairing energy decreases more room for electrons less repulsion.
All 2nd and 3rd row octahedral TM complexes are _________
low spin
Order ligands examples from high spin to low spin increases delta size
Halide donor < O donor < N donor < C donor
Order increasing delta size with respect to pi interactions
Strong pi DONOR < weak pi donor < no pi donor < weak pi acceptor < strong pi acceptor
(weak sigma –> strong sigma)
Which is the orbital arrangement in the tetrahedral complex?
No d orbitals point directly towards ligands as ligands slightly above and below plane.
Which orbitals are more stable in the tetrahedral complex, why?
Dx2-y2 and dz2, point less towards ligands more stable so E is lowered
Which orbitals are less stable in the tetrahedral complex, why?
Dxy, xz, yz as point more towards ligands, repulsion destabilises complex, E raised.
Describe the energy sets for orbitals in tetrahedral ligand feild
Higher: t2 3 orbitals xy xz and yz
lower: e z2 and x2-y2
CFSEtet equation
[(−3/5 xno. electrons in e)+(+2/5 x no. electrons in t2)]DeltaTet+zP
How to D orbitals order in energy for Square planar complex?
Dx2-y2»> dxy > dz2 > dxz=dyz
What factors determine is 4 coordination is square planar or tetrahedral?
Square planar:
First row of TMs with strong field ligands - larger d orbital spitting allowed more electrons at lower energy.
2nd / 3rd row TMs are S.P. larger D orbitals, more repulsive interations with ligands larger d splitting,
What is the Jahn-Teller effect
Systems will remove the degeneracy and undergo distortion to remove the ambiguity of which orbital single electron will occupy.
Which systems does Jahn-Teller effect usually take place?
Mostly octahedral complexes with odd number of electrons occupying eg set. example d9, high spin d4 or low spin d7
Describe orbitals energy for Z elongation Jahn-Teller
Equatorial plane compresses. Z orbitals more stable and so z2 , dxz and dyz will lower in E. lone electron in x2-y2
Describe orbitals energy for Z compression Jahn-Teller
More z orbitals interaction, destabilised, z2, dxz and dyz increase in E. lone electron in z2
