Abstract
The formation of complexes in catalysts of the Ziegler-Natta type are studied virtually in situ using Mössbauer spectroscopy in combination with a quick-freezing technique. Information on the dynamics of the processes involved is acquired without perturbing the state of the systems under study. The mechanism of formation and the nature of the catalytically active complexes are investigated by a method that allows the condition of the catalyst to be observed without removing it from the reaction medium.