TRANSITION-METAL GERMYLENE COMPLEXES IN ZEOLITE CAGES - ANCHORING AND STABILITY

The surface chemistry of the two germylene complexes Cl2(THF)GeM(CO)5 (M = Mo (1) and W (2)) in zeolite Y was studied with X-my absorption spectroscopy (Ge, Mo, W edge EXAFS) and in situ FTIR/TPD-MS techniques. The molybdenum complex 1 interacts with the framework of Na-Y zeolite at room temperature where decarbonylation occurs to a small extent. The intrazeolite 1 retains the Ge-Mo bond up to about 120-degrees-C. In proton-loaded H-Y zeolite, framework interactions with temperature, and the Ge-Mo bond is retained up to about the same temperature. At higher temperatures, the Ge-Mo bond is cleaved and MoClx and Mo-Mo species are formed in the Na-Y and H-Y forms, respectively. GeClx fragments attach to both zoolite frameworks. The intrazeolite complex Cl2(THF)GeW(CO)5 (2) retains all rive carbonyl ligands up to about 100-degrees-C in both Na-Y and the proton form. Significant anchoring through the Ge moiety is observed at room temperature in Na-Y and at about 80-degrees-C in the proton form. The intrazeolite stability of the anchored Ge-W complex is somewhat higher than that of the Ge-Mo analog, and WClx species are formed upon cleavage of the Ge-W bond at higher temperatures. The anchoring of the Cl2(THF)Ge moiety into Na-Y is believed to be based upon a Na+--Cl- interaction between Na ions in zeolite coordination sites and the chloride ligands of the precursor. The only gas evolution detected up to about 120-degrees-C is due to partial decarbonylation (CO) and HCI formation in the acid supports. The absence of precursor desorption confirms the effective anchoring of the transition-metal germylene complexes into zeolite cages.