I1 Flashcards
Why is the group oxidation state never achieved after group 8 in the 3d series?
Due to the increase in ionisation energy with increasing nuclear charge.
What are the common metal geometries for first-row transition metals?
Common geometries include:
* octahedral (Oh)
* tetrahedral (Td)
* square planar (D4h)
What does ligand field theory add to crystal field theory?
Ligand field theory includes a covalent contribution to bonding, whereas crystal field theory is purely electrostatic.
Why do weak field ligands, like Cl-, have a small Δoct?
Weak field ligands donate electron density inefficiently, leading to weak metal-ligand interactions.
What is a spin crossover (SCO) transition?
A reversible transition between high-spin and low-spin states of a metal complex, influenced by temperature, pressure, or light.
What effect do π donor ligands have on Δoct?
π donor ligands decrease Δoct by raising the energy of t2g orbitals through weakly antibonding interactions.
What effect do π acceptor ligands have on Δoct?
π acceptor ligands increase Δoct by lowering t2g orbital energy through bonding interactions.
What is the spectrochemical series?
A ranking of ligands based on their ability to split d-orbital energy levels in a metal complex.
What are the differences between 1st and 2nd/3rd row transition metals?
Key differences include:
* larger coordination numbers
* stronger ligand fields
* lower pairing energy
* increased spin-orbit coupling
* greater metal-metal bonding in 2nd/3rd row metals.
What is the lanthanide contraction?
The progressive decrease in ionic radii across the lanthanide series due to poor shielding by 4f electrons.
Why are lanthanides mostly in the +3 oxidation state?
4f orbitals are tightly bound, making further ionization difficult.
What is charge transfer (CT) in electronic spectra?
A transition where charge is transferred between ligand and metal orbitals, leading to intense absorption bands.
What is the Laporte selection rule?
Transitions within centrosymmetric molecules are forbidden unless there is a change in parity (g ↔ u transitions allowed).
Relaxed- not perfectly centrosymmetric- polydentate ligand, asymmetric vibration- removes centre of symmetry
What determines the spin state of a metal complex?
The relative magnitude of Δoct and pairing energy (P) determines whether a complex adopts a high-spin or low-spin state.
What is a ligand-field spectrum?
An absorption spectrum resulting from electronic transitions within d orbitals split by a ligand field.
What is the Tanabe-Sugano diagram used for?
Predicting electronic transitions and energies in d-block metal complexes.
What does SALE stand for and what is it?
Symmetry Adopted Linear Combinations
Combinations of atomic orbitals that conform to the symmetry of a molecule.
What does it mean that ligand sigma orbitals have no combination that has the symmetry of metal T2G orbitals?
Metal T2G orbitals don’t participate in sigma bonding and eg is weakly antibonding. TT bonds with metal d orbitals include combinations of T2G symmetry allowing T2G to be non-bonding, adjusting the energy of T2G orbitals and delta oct.
What are the MO energy levels of an octahedral complex?
See camera roll
What decreases delta oct?
Pi donor ligands such as Cl, Br, OH, H2O, and weak field ligands.
What increases delta oct?
Pi acceptor ligands such as strong field CN, CO, which accept electron density through vacant pi*.
What are the 3 types of magnetic behaviour?
Diamagnetic- (no unpaired electrons)
Paramagnetic- (unpaired electrons, but not aligned unless in the presence of a magnetic field)
Ferromagnetic- (unpaired electrons, aligned even in the absence of a magnetic field)
What is Spin Crossover?
A reversible magnetic effect where the spin state, magnetic moment of a d-block metal ion can be changed by factors such as temperature, pressure, or light irradiation.
How does spin crossover effect bond distances?
Sensitive to spin state - longer for high spin state due to increased occupancy of eg* orbitals and shorter in low spin state
