Platinum complexes macrobicyclic

Sargeson and co-workers have reported the use of [Pt(en)3]4+ in template reactions to produce the platinum(IV) complexes of the macrobicyclic ligands sep and (N02)2sar (170).477 These reactions are analogous to those that occur around cobalt(III). However, in contrast to the [Co((N02)2sar)]3+ system, reduction of the pendant dinitro groups did not yield amines, but hydroxyamine groups.478... 

Data on the photocatalytic hydrogen-production cycles in systems including different macrobicyclic complexes are systematized in Ref. 384. [Ru(bpy)3], [Ru(4,4 -Me2bpy)3] +, and [Ru(bpy)2L] (L is a carboxylic acid or its derivatives) cations were chosen as sensitizers and EDTA as a sacrificial electron donor. Dependences of hydrogen-production rates and hydrogen yields on the redox potential magnitude, as well as on the concentrations of ETA, sensitizer, and platinum catalyst the irradiation time and the pH of the solution have been studied. 

With a platinum catalyst, methylviologen is undoubtedly a better electron transfer agent than macrobicyclic cobalt complexes. To the contrary, when colloidal RU2O3 (5 x IQ- moM i) deposited on silicon surface is employed as a catalyst, the rate of hydrogen production in the case of [Co(Clsar)]3+ cation is 55 pmolmin-h whereas for methylviologen it is 11 pmol min-i under the same experimental conditions. 

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