Crystal field theory

partially filed d-orbital

Cu, Ag, Au

Ru, Os, Rh, Ir, Pd, Pt

ligands that are C based e.g. CO, CH3

quintuple bond

swapping reaction

bonded directly to metal

electrostatically associated with inner sphere complex

value that never changes oxidation number satisfied by -ve ions

no. of groups covalently bonded to M coordination number directed to fixed positions in space about central M ion

increasingly less favoured L->R Zeff increases IE increases harder to move away from nucleus

becomes increasingly oxidising - wants to be removed

increasingly favoured RDF more diffuse less electron repulsion M easier to oxidise

[simple] based on electrostatics treats ligands as point charges ignores possibility of metal d-electrons being removed in bonding

[more complex] allows for covalent bonding

as ligands approach more closely along x/y/z axis, 3d orbitals lose degeneracy dxy, dxz, dyz = t2g (less electron repulsion; stabilised as they lie between x/y/z axis) dx2-y2 + dz2 = eg (destabilised)

[crystal field stabilisation energy] represents stabilisation relative to spherical field = 0 (stabilisation must offset destabilisation) -> centre of gravity/barycentre

-2/5

3/5

Δoct = 10Dq

[double humped plot of hydration for octahedral M2+ ions] hydration = M2+(g) + H2O -> [M(H2O)6]2+ expected trend = increased favourable (exothermic) L->R as Zeff increases; ion size decreases ; M-L interaction increases measured trend = Ca2+, Mn2+, Zn2+ sit on line - others vary significantly related to Δoct (makes favourable contribution to hydration energy of system - more exothermic)

d1-d3 = no choice d4 = either keep filling or double one of t2g sets -although t2g gives -2/5 Δoct, filling doubly filled orbital increases e- repulsion

[weak field arrangement] energy to put e- in eg set < e- repulsion

[strong field arrangement] energy to put e- in eg set > e- repulsion