Bis-pocket porphyrins

We have already seen that sterically encumbered porphyrins may still be susceptible to p-0X0 bridge formation if any four-coordinate species in solution binds oxygen on the open face. Steric encumbrance on both faces of the porphyrin, as in the bis-pocket porphyrin systems of Amundsen and Vaska and Suslick may prevent this bimolecular oxidation pathway. 

Suslick and his coworkers examined the shape selective oxidation of alkanes and alkenes catalyzed by the iron and manganese complexes of the bis-pocket porphyrin (Mn(TTPPP) and Fe(TTPPP) where TTPPP is tetrakis(2,4,6-triphenylphenyl)porphyrin) with a variety of oxidants such as mCPBA, PhIO, F5-PhIO [290]. The selectivities for terminal hydroxylation of n-alkanes are found to be very similar. While the details of the reactive intermediates are not clear, a peracid-Fe TTPPP adduct was obtained as a stable complex at -78°C to measure IR spectrum (Vc=o- 1744 cm l) [139]. However, an expected structure of an oxidant-metalloporphyrin complex could be too crowded to react with olefins. Uponwarming the solution temperature up to room temperature, the... 

TPP tetraphenyl porphyrin, OETPP 2,3,7,8,12,13,17,18-octaethyl-5,10,15,20-tetraphenyl-porphyrin, OEP octaethylporphyrin, TipsiPP 5,10,15,20-tetrakis(2, 6 -bis(triisopropylsiloxy) phenyl)-porphyrin (in short bis-pocket siloxyl porphyrin)... 

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