The Development of Platino-Calixarenes TRAPPING PLATINUM HYDRIDES IN MOLECULAR CAVITIES

Hydrido complexes, especially of the platinum group metals, have a pivotal role in homogeneous catalysis (1). They appear as intermediates in many catalytic cycles, including hydroformylation, asymmetric hydrogenation, hydroxycarboxylation, and oligomerisation of olefins. In order to perform highly selective hydrido-mediated catalytic reactions it is essential that ligands are present which allow both fine-tuning of the M-H bond reactivity and proper discrimination of incoming substrates, with thc latter being especially important for enantioselectivity. A major limitation of presently available platinum metal hydride catalysts concerns the freely accessible reactive metal centre. With such species, there is no easy way to discriminate between incoming substrates of different shape. A difficult challenge to be overcome during the development of the next generation of hydride catalysts is to locate the platinum metal hydrides inside well-defined