Soluble molecular catalysts have the disadvantage of a certain instability, particularly under the sometimes extreme conditions required for small-molecule activation. This instability can result in the release of metal ions and their transformation into nanoparticles or metal colloids. Although these compounds may be formed in very small quantities, they may in fact be powerful catalytic entities, so that the reaction observed is not due to the initial molecular catalyst but to the solid compounds derived from it. This has led to many misinterpretations in the literature and to much controversy. The lecture is based in detail on examples that are highly representative of this problem and show that some molecular catalysts are in fact no more than " precatalysts ".
Nevertheless, these observations open up new prospects for the synthesis of heterogeneous catalysts from organometallic complexes. Indeed, the choice of the precatalyst, its metal and its ligand, which can by synthesis be easily modified, has a considerable impact on the structure and reactivity of the solids derived from it. This concept is developed in the lecture.
