Evaluation of the role of organometallic species in the chemistry of interstellar and circumstellar media

Interactions between metal atoms or ions and unsaturated organic molecules in the interstellar or circumstellar media could play an important role in the chemistry of these media.Ab‐initio calculations were performed to predict bonding energy of the cations [metal‐benzene]+ and [Mg‐pyrene]+. We showed that the higher bonding energy of [metal‐benzene]+ is, the larger is the metal depletion. This result should be extended to bigger PAHs. We conclude that organometallic chemistry can participate to the depletion of metals.We synthetized grains composed of small cristallized cores of metal (diameter from 20A to 200A) embedded in pyrene. The mean diameter of grains depends of the ratio pyrene/metal.Finally, we showed that organometallic reactions can be catalytic. Large organic molecules could be synthetized faster in the ISM through such this process than through classical collisions. We propose that the first ring of PAH molecules could be synthetised in this way.