TMC

splitting in octahedral complexes

highest: z², x²-y²

lowest: xy, xz, yz

splitting in tetrahedral complexes

highest: xy, xz, yz

lowest: z², x²-y²

splitting in square planar complexes

highest: x²-y²

high: xy

mid: z²

lowest: xz, yz

reasons for tet being preferable

• sterically favoured

  • large ligands

• electronically unfavourable

  • less CFSE as ∆t is small

  • e- likely to be unpaired (high spin)

reasons for sp being favoured

• favoured electronically

  • ∆sp is large so more CFSE

  • e- likely to be paired

• unfavoured sterically

  • less space for ligands

• high field ligands where ∆ is large enough to overcome steric

complex of any metal when in any aqueous solution

[M(H2O)₆]ⁿ⁺

usual spin with H2O ligand

high spin (water is weak field ligand)

comparison between ∆o and ∆t

2/5 ∆t = 1/5 ∆o

effect of oxidation state on spin state

• increasing OS decreases E of metal orbitals

• More well-matched with ligand orbitals

• Better overlap splits t2g and eg more

• Increases ∆

• more likely to by LS

effect of ligand on spin state

• high field ligands split t2g and eg more

• more likely to be LS

likely reason for different properties when OS increases

• ∆ is larger

• electrons adopt LS configuration

• JT distortion

compression vs elongation (JT distortion)

compression

• -1/3 δ, +2/3 δ

elongation

• -2/3 δ, +1/3 δ

reason for magnetic moment changing during oxidation/reduction

changes to whether e- are paired or unpaired

paramagnetic

unpaired e-

diamagnetic

paired e-

paramagnetic vs diamagnetic

paramagnetism has 100x greater effect

requirement of JT distortion

asymmetric occupation of e- orbitals

effects down a triad for [M₂L₉] complex

top: contracted orbitals, no M-M bond

mid/btm: bigger orgbitals, M-M bonds form from better overlap

Hard species

• high charge density

• bonds ionically

soft species + bonding

• low charge density

• bonds covalently

Properties of linear ligands

• sp hybridised

• probably ionic interactions

• minimises sterics

properties of bent ligands

• sp2 or sp3 hybridised

• probably maximises orbital overlap

MO basis of 18e- rule

• sigma diagram

  • a1g, t1u, eg, t2g are 9 bonding MOs, 2e- each

• pi diagram

  • t2g now split, still 9 bonding MOs

Bonding of H₂ ligand

• sigma donation

  • donates from middle of H-H bond

• pi accepting

  • accepts e- into H-H σ*

  • will weaken H-H bond

• Synergic

effect of adding pi donating ligand to complex on CO

• ligand donates more e- density onto metal

• more e- density able to be donated to CO

  • increased backbonding

• weakens bond

things to consider with non-aromatic conjugated rings

• can still act like Cp

  • 2 =’s can link up and become η3

• can be boat-like and bend

IR of free CO

2143 cm-1

how energies of 3d orbitals are affected by ligands

energies are raised if they point towards ligands due to e-e repulsion, lowered if directed away

how to remove Ni from the middle of a complex

HCl, forms NiCl2 and protonates ligand

why are hard-hard interactions favoured over soft-hard

maximises ionic interactions

how alkynes coordinate to metals

sigma donor

• donates from C-C pi bond

pi acceptor

• accepts into c-c pi*

both weaken the C-C bond

how can the alkyne change during coordination

• bond triangle-like as an alkene and 2 single bonds

• gradual change from sp to sp2

• lengthens c-c bond

• decreases bond angle

how to detect changes to alkyne triple bond as it coordinates

IR

• triple bond frequency decreases

diffraction

• bond length and angles changing

what is alkene insertion

alkene added to reaction

what is CO insertion

CO is added to reaction

what is reductive elimination

metal complex loses 2 ligands, decreasing the Ms OS and coordination number

what is ligand addition

when a ligand is added to the metal complex, but the metal OS doesnt change

difference between pi acceptor and pi donator MO diagrams

acceptor

• higher E

• worse overlap

• splits t2g more

• larger ∆ between t2g and eg*

donator

• lower E

• better overlap

• t2g split less (equal contributions)

• ∆ less between t2g* and eg*