Intrazeolite metal carbonyl kinetics. Substitution reaction of MO([sup 12]CO)[sub 6] in sodium zeolite Y
- Univ. of Toronto, Ontario (Canada)
The first quantitative and detailed kinetic study of simple thermal reactions of a molecule encapsulated in a zeolite cavity is reported. Substitution reactions of Mo([sup 12]CO)[sub 6] with PMe[sub 3] in the [alpha]-cages of a Na[sub 56] Y zeolite host proceed cleanly to form cis-Mo(CO)[sub d](PMe[sub 3])[sup 2] by what are essentially pseudo-first-order dissociative and associative processes. Reactions with [sup 13]CO proceed only by the dissociative path, which is 10[sup 3] times faster than corresponding reactions in homogeneous solution. Dissociative substitution by PMe[sub 3] is retarded by applied pressures of [sup 12]CO, as expected, but it is also retarded to a significant extent by increased Mo(CO)[sub 6] and PMe[sub 3] loadings. Substitution by [sup 13]CO is similarly retarded by increasing pressures of the entering [sup 13]CO. The activation parameters, [Delta]H[sub d] = 61 [plus minus] 5 kJ mol[sup [minus]1] and [Delta]S[sub d] = -139 [plus minus] 15 J K[sup [minus]1] mol[sup [minus]1]/, are unusual for a dissociative process but can be interpreted on the basis of structural information concerning pertinent reactant and product guests obtained mainly from FT-mid-IR, EXAFS, and DOR-MAS-NMR analytical methods. The kinetics data reveal that the [alpha]-cages of Na[sub 56]Y provide precisely defined activating environments of a unique kind. From a coordination chemistry point of view, these nanoreactors appear to behave as macrospheroidal multidentate multisite anionic ligands (which we call zeolates) toward extraframework charge-balancing cations to which metal carbonyl reactant, product, and ligand guests can become attached. The best model that emerges from this study pictures a supramolecular assembly of Mo([sup 12]CO)[sub 6] and PMe[sub 3], [sup 13]CO, or [sup 12]CO, housed within the [alpha]-cage of Na[sub 56]Y, anchored to extraframework Na[sup +] cations, and subject to loading-dependent cooperative interactions. 38 refs., 13 figs., 8 tabs.
- OSTI ID:
- 6258842
- Journal Information:
- Journal of the American Chemical Society; (United States), Vol. 115:4; ISSN 0002-7863
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
CARBON MONOXIDE
ENCAPSULATION
REACTION KINETICS
MOLYBDENUM COMPLEXES
PHOSPHORUS COMPOUNDS
EXPERIMENTAL DATA
NUCLEAR MAGNETIC RESONANCE
SPECTROSCOPY
STOICHIOMETRY
TEMPERATURE DEPENDENCE
ZEOLITES
CARBON COMPOUNDS
CARBON OXIDES
CHALCOGENIDES
COMPLEXES
DATA
INFORMATION
INORGANIC ION EXCHANGERS
ION EXCHANGE MATERIALS
KINETICS
MAGNETIC RESONANCE
MATERIALS
MINERALS
NUMERICAL DATA
OXIDES
OXYGEN COMPOUNDS
RESONANCE
SILICATE MINERALS
TRANSITION ELEMENT COMPLEXES
400201* - Chemical & Physicochemical Properties
400102 - Chemical & Spectral Procedures