TOPOTACTIC METAL-ORGANIC CHEMICAL-VAPOR-DEPOSITION IN ZEOLITE-Y - STRUCTURE AND PROPERTIES OF CH3MY FROM MOCVD REACTIONS OF (CH3)2MHY, WHERE M = ZN, CD

A mild and controlled synthetic route has been developed that quantita tively incorporates MOCVD-type precursors within the void spaces of ze olite Y. The process is illustrated with respect to the reactions of v olatile, molecular dimethylcadmium and dimethylzinc with Bronsted acid sites in zeolite Y. Charge-balance and templating constraints of the host ensure that the sole reaction product CH3M (M = Cd, Zn) is exclus ively housed in the supercages of zeolite Y with spatial and compositi onal uniformity throughout the entire host lattice. These anchored CH3 M species are perfectly poised for assembly reactions with volatile ch alcogenide reagents to form ordered superlattices of II-VI semiconduct or nanoclusters. The geometry, site location, and occupancy of anchore d CH3M have been determined by Rietveld analysis of low-temperature sy nchrotron powder X-ray diffraction data. For samples chemically analyz ed as containing 44 CH3M moieties per unit cell of zeolite Y, almost e qual numbers of CH3M Species are found to be anchored via the metal ce nter to framework oxygens at sites II and III, located exclusively in the supercage. The transformation from HY to CH3MY host has been conve niently monitored by in situ mid-IR and far-IR spectroscopy. Distincti ve vibrational modes are assignable to intrazeolite (CH3)2M, anchored CH3M, and evolved CH4 species. Room temperature C-13 and Cd-113 static and MAS-NMR studies of these species reveal that they are undergoing motion on the NMR time scale in the supercages of zeolite Y. Observed NMR chemical shifts are consistent with primary anchoring interactions between the metal center and the oxygen framework for both chemisorbe d (CH3)2MNaY and anchored CH3MY species. In the case of the former, Na -23 MAS-NMR spectroscopy reveals the existence of a secondary anchorin g interaction between supercage site II Na+ cations and the nucleophil ic methyl groups of the (CH3)2M guest.