Non-covalent binding of water reduction catalysts and photosensitizers to hydrophobic silica particles represents a general approach for heterogenizing molecular water splitting components.

2-Aminopyridines are key structural cores of bioactive natural products, medicinally important compounds, and organic materials and thus, extremely valuable synthetic targets. The few reported 6-substituted 2-aminopyridines and the lack of flexible, efficient and general applicable methods for their synthesis demonstrates the urgent need of new methods for their preparation. Reactions between 2,6-dibromopyridine and primary or secondary, cyclic or acyclic, and aliphatic or aromatic amines were shown to selectively yield the respective 6-bromopyridine-2-amines in very high yields which were successfully used as substrates for subsequent C À C cross-coupling reactions. The recently introduced dichloro-bis[1-(dicyclohexylphosphanyl)piperidine]palladium (1) was used as catalyst for the cross-coupling of 6-bromopyridine-2-amines with arylboronic acids, diaryl-and dialkylzinc reagents or olefins and hence, is also an excellent C À C cross-coupling catalyst for this type of substrate. Moreover, all the reaction protocols presented were in each of the catalyses uniformly applied. The scope of both the amination and the cross-coupling reactions are well defined and allow one to simply adapt the reaction protocols directly to other amines and/or coupling partners and, thus, provide for the first time a very flexible and generally applicable reaction protocol to get access to 2-aminopyridines.

A series of complexes of the type [fac‐Re(X)(CO)3(N∩N)] (X = –C≡C–R, N∩N = 2,2′‐bipy, 2,2′‐phen) were synthesized and fully characterized. Their photophysical characteristics make them very convenient photosensitizers (PSs). Upon light irradiation, H2 formation was observed for all alkynyl complexes in the presence of a water‐reducing catalyst (WRC) and a sacrificial electron donor. Relative rates of H2 production indicate a dependency upon the diimine ligands rather than upon the nature of the σ‐bonded alkynyl derivatives. The coordinated acetylene group induces a redshift of the λmax of the MLCT band in UV/Vis spectroscopy as compared to those of the corresponding halides, nitriles, or cationic ReI complexes, such as [fac‐ReX(CO)3(N∩N)] (X = pyridine, H2O, N∩N = bipy, phen).

Dichloro[bis{1-(dicyclohexylphosphanyl)piperidine}]palladium [(P{(NC(5)H(10))(C(6)H(11))(2)})(2)PdCl(2)] (1) is a highly active and generally applicable C-C cross-coupling catalyst. Apart from its high catalytic activity in Suzuki, Heck, and Negishi reactions, compound 1 also efficiently converted various electronically activated, nonactivated, and deactivated aryl bromides, which may contain fluoride atoms, trifluoromethane groups, nitriles, acetals, ketones, aldehydes, ethers, esters, amides, as well as heterocyclic aryl bromides, such as pyridines and their derivatives, or thiophenes into their respective aromatic nitriles with K(4)[Fe(CN)(6)] as a cyanating agent within 24 h in NMP at 140 °C in the presence of only 0.05 mol % catalyst. Catalyst-deactivation processes showed that excess cyanide efficiently affected the molecular mechanisms as well as inhibited the catalysis when nanoparticles were involved, owing to the formation of inactive cyanide complexes, such as [Pd(CN)(4)](2-), [(CN)(3)Pd(H)](2-), and [(CN)(3)Pd(Ar)](2-). Thus, the choice of cyanating agent is crucial for the success of the reaction because there is a sharp balance between the rate of cyanide production, efficient product formation, and catalyst poisoning. For example, whereas no product formation was obtained when cyanation reactions were examined with Zn(CN)(2) as the cyanating agent, aromatic nitriles were smoothly formed when hexacyanoferrate(II) was used instead. The reason for this striking difference in reactivity was due to the higher stability of hexacyanoferrate(II), which led to a lower rate of cyanide production, and hence, prevented catalyst-deactivation processes. This pathway was confirmed by the colorimetric detection of cyanides: whereas the conversion of β-solvato-α-cyanocobyrinic acid heptamethyl ester into dicyanocobyrinic acid heptamethyl ester indicated that the cyanide production of Zn(CN)(2) proceeded at 25 °C in NMP, reaction temperatures of >100 °C were required for cyanide production with K(4)[Fe(CN)(6)]. Mechanistic investigations demonstrate that palladium nanoparticles were the catalytically active form of compound 1.

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