Polymers norbornadiene-quadricyclane

The polymer cobalt containing prophyrins (32), (33) were used in the photochemical energy storage system norbomadiene-quadricyclane (Eq. IS) This system for storage of solar energy is useful because of the high AH value between the two valence isomers on one side and the low price for the starting material (norbornadiene) on the other side. 

Table 6. Recycling studies using polymer Co-porphyrin (55) for the conversion of quadricyclane at 303 K to norbornadien. 0.1 g catalyst (0,44 % Co) in 10 ml xylene containing 1 M quadricyclane. k normalized value to 1 g catalyst to 11 solution...

These observations suggested that Pd (II) chloride bound to phosphine-substituted polystyrene might be an eflFective catalyst for the conversion of quadricyclane to norbornadiene. We therefore investigated the preparation of such a polymer-anchored phosphine Pd (II) chloride catalyst. 

Low molecular weight Schiff base complexes of many metals are well known and in the case of aromatic ligands these tend to have high thermal stability. Polymeric Schiff bases likewise have been well reported, and although many of these have the Schiff base appended as a substituent on a vinyl polymer backbone, others have the Schiff base residue as part of the mainchain. The latter continue to complex metals very well [140, 141] and one early paper reports the use of a Mn(II) polymeric complex in the aerobic oxidation of cumene at 30-100°C [142]. Indeed there is an implication in the paper that the polymer complex is stable to 200°C when complexed O2 tends to be liberated. Wohrle s group have also studied polymeric Schiff bases extensively, again mostly with pendant groups. However, they have reported a mainchain poly Schiff base [143], its complexation with Co(II), Ni(II) and Cu(II), and use of the supported complexes as catalysts in quadricyclane isomerisation to norbornadiene. 

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