Electron paramagnetic resonance investigations of CO adsorption on RuY zeolite

The adsorption of carbon monoxide onto ruthenium exchanged into NaY zeolite has been investigated by CW-EPR techniques using (13) C-enriched CO. A low spin eta (1){Ru(3cCO}(5) adduct with g = 2.065, g\\ = 1.987 and |A((99)Ru) = 1.3 mT, |A||(99)Ru) = 1.7 mT, |A_|(101 Ru) = 1.5 mT, A||(101)Ru) = 1.9 mT and |A|(13)C) = 6.0, |A|| |(13)C) = 6.8 mT has been identified. The magnetic parameters have been analyzed in terms of the molecular structure and spin density distribution. The results are consistent with an apical coordination of CO and the bonding established by the overlap between d(z)z2 and 5 sigma orbitals. The eta{RuIII (3c)CO}(5) adduct can be classified as a a metal-centred radical located in SIl'/SII sites. The spin density on Ru is equal to 0.6 and is confined mainly to the dz(2) orbital and 0.1 on carbon atom of the CO ligand.