Search

A series of ruthenium [NNN]- or [NCN]-type complexes (3–7) bearing PPh3 ancillary ligands have been synthesized from pyridine- or phenylene-bridged bis(triazoles) 1 and 2. In the case of [NNN]-pincer complex 3, an unusual and unexpected cis-orientation adopted by two sterically demanding PPh3 ligands was observed, and such configuration proved to be unchanged in solution for a long time. By contrast and as expected, the two phosphines are found to be trans to each other in the case of [NCN]-type pincer complex 4, but an oxidation of RuII center to RuIII occurred. Complex cis-3 underwent ligand exchanges leading to the formations of diphosphine derivatives 5 and 6. As a representative, cis-3 was treated with the base in isopropanol affording a mixture of Ru–hydrido complexes with various phosphine binding modes, one of which (trans-7) bearing two trans-standing phosphines has been successfully isolated and fully characterized. The catalytic performances of all newly synthesized Ru complexes have been examined and compared in transfer hydrogenations of ketones and enones, in which mono-phosphine complexes proved to be significantly superior to their diphosphine counterparts. The catalytic process proved to involve Ru–H key intermediates, but the trans-oriented Ru–H species is unlikely to be the main catalytic contributor. In particular, the best performer cis-3 exhibits high chemoselectivity in certain cases catalyzing α,β-unsaturated ketones, whose behavior is quite different compared to most precedents.

The first phthalocyanine (Pc) macrocycle-containing [FeFe]-hydrogenase model complex, (i-BuO)8PcRu(CO)(μ-PDT)[(Ph2P)2NCH2C5H4N]Fe2(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)2NCH2C5H4N (1), whereas further treatment of 1 with diiron complex (μ-PDT)Fe2(CO)6 in refluxing o-xylene produced the 4-picolylazadiphosphine-chelated diiron complex (μ-PDT)[(Ph2P)2NCH2C5H4N]Fe2(CO)4 (2). While 3,6-dihydroxyphthalonitrile reacted with i-BuBr/K2CO3 in DMF at 80 °C to give 3,6-diisobutoxyphthalonitrile 3, further reaction of 3 with lithium wire in refluxing i-BuOH afforded isobutoxyphthalocyanine (i-BuO)8PcH2 (4). Furthermore, 4 reacted with Ru3(CO)12 in refluxing PhCN to give ruthenium phthalocyanine (i-BuO)8PcRu(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 ...

Two new ferrocenyl (Fc) group containing 1,5-diaza-3,7-diphosphacyclooctane ligands, PFc2NAr2 (1, Ar = Ph; 2, Ar = p-BrC6H4), were prepared by reaction of FcPH2 with 2 equiv of paraformaldehyde in glycol followed by treatment of the resulting FcP(CH2OH)2 with 1 equiv of aniline or p-bromoaniline in 79% and 67% yields, respectively; however, ligands 1 and 2 could be also prepared by treatment of the isolated and purified FcP(CH2OH)2 with 1 equiv of aniline or p-bromoaniline under similar conditions in 80% and 72% yields, respectively. Further treatment of 1 or 2 with the complex salt [Ni(MeCN)6](BF4)2 in MeCN at room temperature resulted in formation of the first ferrocenyl-containing complexes [Ni(PFc2NAr2)2](BF4)2 (3, Ar = Ph; 4, Ar = p-BrC6H4) in 95% and 90% yields, respectively. Compounds 1–4 were structurally characterized by elemental analysis and spectroscopy and particularly for 1, 2, and 4 by X-ray crystallography. When the cyclic voltammetric behavior of 1–4 was investigated, 3 and 4 were found t...

The first two model compounds for [FeFe]-hydrogenases that contain a subphthalocyanine (SubPc) macrocycle, namely, [{(μ-SCH2)2N(CH2)2CO2-3-C6H4S2C6H4-3′-O(SubPc)}Fe2(CO)6] (5) and [{(μ-SCH2)2NC6H4-4-O(SubPc)}Fe2(CO)6] (8), have been synthesized and structurally characterized. The treatment of chlorosubphthalocyanine (SubPc-Cl, 1) with (3-HOC6H4S)2 in toluene gave the corresponding phenoxy-substituted SubPc derivative 3-HOC6H4S2C6H4-3′-O(SubPc) (2) in 78 % yield, whereas the reaction of in-situ-generated [(μ-HOCH2S)2Fe2(CO)6] (3) with β-alanine afforded diiron complex [{(μ-CH2S)2N(CH2)2CO2H}Fe2(CO)6] (4) in 53 % yield. Further treatment of 2 with 4 in the presence of N,N′-dicyclocarbodiimide (DCC) and N,N-dimethyl-4-aminopyridine (DMAP) in CH2Cl2 resulted in the formation of model compound 5 in 86 % yield. Model compound 8 could be prepared by two methods. One method involves the reaction of in-situ-generated 3 with 4-aminophenol in tetrahydrofuran (THF) to give diiron complex [{(μ-CH2S)2NC6H4OH-4}Fe2(CO)6] (6) in 61 % yield and further treatment of SubPc-Cl (1) with 6 in toluene to give 8 in 13 % yield. The other method involves the reaction of SubPc-Cl (1) with silver triflate (AgOTf) followed by treatment of the resulting intermediate SubPc-OTf (7) with 6 in the presence of Et3N to produce 8 in a much higher yield (59 %). All the new precursors (2, 4, and 6) and the model compounds 5 and 8 have been fully characterized by elemental analysis and various spectroscopy techniques, as well by X-ray crystallography for 2, 4, 6, and 8. In addition, the photoinduced H2 production catalyzed by model 8 was preliminarily investigated.

The [3 + 2] cycloaddition reaction of C(60) with ethyl isonicotinoylacetate in the presence of piperidine in PhCl at room temperature or in the presence of Mn(OAc)(3) in refluxing PhCl gave the pyridyl-containing dihydrofuran-fused C(60) derivative (4-C(5)H(4)N)C(O)═C(C(60))CO(2)Et (1), whereas the phenyl-containing C(60) derivative PhC(O)═C(C(60))CO(2)Et (2) was similarly prepared by [3 + 2] cycloaddition reaction of C(60) with ethyl benzoylacetate in the presence of piperidine or Mn(OAc)(3). More interestingly, one of the new porphyrin-fullerene dyads, i.e., [4-C(5)H(4)NC(O)═C(C(60))CO(2)Et]·ZnTPPH (3, ZnTPPH = tetraphenylporphyrinozinc), could be prepared by coordination reaction of the pyridyl-containing C(60) derivative 1 with equimolar ZnTPPH in CS(2)/hexane at room temperature. In addition, the β-keto ester-substituted porphyrin derivative H(2)TPPC(O)CH(2)CO(2)Et (4) was prepared by a sequential reaction of HO(2)CCH(2)CO(2)Et with n-BuLi in 1:2 molar ratio followed by treatment with H(2)TPPC(O)Cl in the presence of Et(3)N and then hydrolysis with diluted HCl, whereas the porphyrinozinc derivative ZnTPPC(O)CH(2)CO(2)Et (5) could be prepared by coordination reaction of 4 with Zn(OAc)(2) in refluxing CHCl(3)/MeOH. Particularly interesting is that the second new porphyrin-fullerene dyad H(2)TPPC(O)═C(C(60))CO(2)Et (6) could be prepared by [3 + 2] cycloaddition reaction of 4 with C(60) in the presence of piperidine in PhCl at room temperature. In addition, treatment of 6 with Zn(OAc)(2) in refluxing CHCl(3)/MeOH afforded the third new dyad ZnTPPC(O)═C(C(60))CO(2)Et (7). All the new compounds 1-7 were characterized by elemental analysis and various spectroscopic methods and particularly for 2, 3, and 5 by X-ray crystallography. The five-component system consisting of an electron donor EDTA, dyad 3, an electron mediator methylviologen (MV(2+)), the catalyst colloidal Pt, and a proton source HOAc was proved to be effective for photoinduced H(2) evolution. A possible pathway for such a type of H(2) evolution was proposed.