Spectroscopy
Infrared spectroscopy can be used to analyse the products of oxidative addition to Vaska's complex because the reactions induce characteristic shifts of the stretching frequency of the coordinated carbon monoxide. These shifts are dependent on the amount of π-back bonding allowed by the newly associated ligands. The CO stretching frequencies for Vaska's complex and oxidatively added ligands have been documented in the literature.
- Vaska's Complex: 1967 cm−1
- Vaska's + O2: 2015 cm−1
- Vaska's + MeI: 2047 cm−1
- Vaska's + I2: 2067 cm−1
Oxidative addition to give Ir(III) products reduces the π-bonding from Ir to C, which causes the increase in the frequency of the carbonyl stretching band. The stretching frequency change depends upon the ligands that have been added, but the frequency is always greater than 2000 cm−1 for an Ir(III) complex.
Read more about this topic: Vaska's Complex