Bimetallic Complexes in Zeolites: Reactivity of Tetracarbonyl(trimethylstanny1)cobalt in Acidic Zeolite Y

Stabilization techniques for low-valent organometallic species in acidic forms of large-pore zeolite Y are reported. The intrazeolite surface chemistry and thermal stability of MesSnCo(CO)4 in HY zeolites (I&NaloA155Si1370384 and H16Na39A155Sil370384) were studied with X-ray absorption spectroscopy (Sn, Co edge EXAFS) and in-sifu FTIR/TPD-MS techniques. The acidic zeolite Y host offers a chemically reactive surface that can interact with the Me3Sn moiety of the bimetallic complex. FTTR and EXAFS data indicate attachment of the complex to the zeolite framework. The intrazeolite SnCo complex is accessible toward carbonyl substitution with PMe3. One observes growing attachment of the precursor (progressive substitution of methyl ligands at tin) to the zeolite with increasing temperature, while the Sn-Co bond and the Co-carbonyl moiety remain stable up to about 90 "C. At higher temperatures the Sn-Co bond is cleaved, the carbonyl ligands are dissociated, and cobalt is oxidized in a reaction with the zeolite protons. The resulting cobalt ions attach to the zeolite framework. InfraredRPD studies show that the SnCo complex reacts differently in the HY zeolite when containing only 16 protons per unit cell and that its decomposition results in metal clusters.