1: Theory of Ligand Exchange Mechanisms Flashcards
Which mechanisms have a detectable intermediate
Id and D
Which of the ligand exchange mechanisms involve the leaving group detaching, or beginning the process of detaching, before the incoming ligand interacts with the transition metal?
D and Id
What technique is most commonly used to follow the kinetics of water exchange in hexaaqua metal complex ions?
Isotope labelling studies combined with NMR spectroscopy
What technique is most commonly used to to follow the kinetics of ligand exchange in a transition metal complex where one ligand is replace by another ligand of a different type?
UV-Vis spectrometry
For which dn configuration would you expect ligand exchange reactions in octahedral complexes to occur at the slowest rate?
d6 Low Spin ∵ fully occupied t2g maximises CFSE. ∴ higher energy barrier to overcome TS and RoR is v. slow
What is the crystal field stabilisation energy for a high spin d4 cation in an octahedral complex?
-0.6Δo
the three electrons in the t2g set of orbitals are each stabilised by -0.4 Δo, while the fourth electron in the eg set is desabilised by +0.6 Δo
What is the crystal field stabilisation energy for a low spin d7 cation in an octahedral complex?
-1.8 Δo + P
d7 Low Spin there one extra pairing energy compared to if the complex was High Spin.
which mechanism does not have a limiting rate
A
an associatve mechanism has a bimolecular rate expression for all concentrations of incoming ligand, Y.
The rate of a ligand exchange reaction depends on
magnitude of ΔG# (i.e. for the transition state) only
what does magnitude of ΔG# dictate?
height of the energy barrier to form the intermediate
what does ΔG# relate?
kinetic rate achieving the equilibrium position
for low charge density we expect
to be labile
high charge density we expect
to be inert
increase of CFSE we expect
to be labile
loss of CFSE we expect
to be inert
