5. Reaction through dissociative mechanism
Outer orbital complexes
sp3d2 hybridization, larger and weaker M-L bonds (higher
energy)
Inner orbital complexes
d2sp3 hybridization, shorter and stronger M-L bonds (lower
energy)
Inner orbital complexes: Inert always
Outer orbital complexes: Labile always
6. Reaction through associative mechanism
Outer orbital and inner orbital complexes with low lying
unhybridized metal d-orbitals.
These orbitals are center attack by the incoming ligand in
associated mechanism of substitution.
Inert complexes
Electrons are present in the unhybridized d-orbitals.
Labile complexes
Vacant unhybridized d-orbitals.
[MnCl6]3- = Labile
[Cr(CN)6]3- = Inert
d2sp3
XX XX XX XX XX XX
XX XX XX XX XX XX
sp3d2
11. Dissociative mechanism: Square pyramidal intermediate
Loss in CFSE = CFSE of SP – CFSE of Oh
Associate mechanism: Pentagonal bipyramidal transition state
Loss in CFSE = CFSE of PBP – CFSE of Oh
If the loss in CFSE negative = inert complex
If the loss in CFSE positive or zero = labile complex
Basolo and Pearson calculated CFSE for LS and HS square
pyramidal and pentagonal bipyramidal complexes.