The Selective Partial Oxidation of Alkanes using Zeolite Based Catalysts. Phthalocyanine (PC) “Ship-in-Bottle” Species

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Abstract
Phthalocyaninatoiron (FePc) complexes may be prepared inside the pore structure of large pore zeolites X or Y by a process of sequential introduction of components followed by assembly inside the void space of the zeolite. Such species are capable of performing as catalysts in the oxidation of alkanes using iodosobenzene as the oxygen atom transfer reagent. The fact that such catalysis is constrained to occur inside the size- and shape-selective zeolite crystallites imposes unique selectivities on the distribution of oxidized products. These catalysts prefer to oxidize the smaller of two competitive substrates and to oxidize toward the ends of the long molecular axis of such substrates. In addition. stereoselectivity is apparent in cases of oxidations with diastereotopic C–H bonds. All of the observed selectivities can be explained in terms of the sieving and orienting effects of the zeolite hosts. While selectivities are moderate with the native zeolites, they may be considerably adjusted by simply altering the charge compensating cations which have the effect of fine tuning the pore dimensions. In the best case, this can lead to a substrate selectivity of 10: I favoring cyclohexane over cyclododecane. In all cases, however, rates of reaction are extremely slow and pore blockage leads to shut-down of the reactivity after few catalytic cycles.