Novel Ruthenium Phthalocyanine-Containing Model Complex for the Active Site of [FeFe]-Hydrogenases: Synthesis, Structural Characterization, and Catalytic H2 Evolution

The first phthalocyanine (Pc) macrocycle-containing [FeFe]-hydrogenase model complex, (i-BuO)(8)PcRu(CO)(mu-PDT)[(Ph2P)(2)NCH2C3H4N]Fe-2(CO)(4) (6), has been prepared by a multistep synthetic route. The treatment of 4-picolylamine with Ph2PCl/Et3N in CH2Cl2 at room temperature gave 4-picolyl-substituted azadiphosphine (Ph2P)(2)NCH2C5H4N (1), whereas further treatment of 1 with diiron complex (mu-PDT)Fe-2(CO)(6) in refluxing o-xylene produced the 4-picolylazadiphosphine-chelated diiron complex (mu-PDT)[(Ph2P)(2)NCH2C3H4N]Fe-2(CO)(4) (2). While 3,6-dihydroxyphthalonitrile reacted with i-BuBr/K2CO3 in DMF at 80 degrees C to give 3,6-diisobutoxyphthalonitrile 3, further reaction of 3 with lithium wire in refluxing i-BuOH afforded isobutoxyphthalocyanine (i-BuO)(8)PcH2 (4). Furthermore, 4 reacted with Ru-3(CO)(12) in refluxing PhCN to give ruthenium phthalocyanine (i-BuO)(8)PcRu(CO)(2) (5). Finally, CO substitution reaction of 5 with diiron complex 2 in the presence of Me3NO in CH2Cl2 resulted in formation of the targeted model complex 6. While all the new compounds 1-6 were structurally characterized, complex 6 was found to be a catalyst for photoinduced H-2 generation.