Band 8, Heft 1-2

Sulfur-based ligands, principally cysteinate, methionine and sulfide, are found in many metallo­enzymes. As these enzymes operate in a protic environment and (in some cases) involve substrates being transformed by sequences of electron and proton transfer reactions, it is important to understand the protonation chemistry of these sulfur-based ligands. In this review, the mechanisms and proton transfer rates of both coordinated thiolates and sulfides are presented, with a particular emphasis on synthetic Fe-S-based clusters. The protonation of natural Fe-S-based clusters is considered in the light of the studies on the synthetic models.

Chemistry of metal and non-metal fluorides in liquid ammonia is often severely hampered, due to the low solubility of inorganic fluorides. This can be overcome by applying either strongly oxidizing fluorides, appropriate fluoride ion acceptors, or by the reduction or conversion of fluorides using solvated electrons. The article summarizes the state-of-the-art of the chemistry of inorganic fluorides in liquid ammonia, with special emphasis on compounds of beryllium, silver and uranium.

O-O bond formation is one of the key reactions that ensure life on earth. Dioxygen is produced in photosystem II, as well as in chlorite dismutase. The reaction mechanisms occurring in the enzyme active sites are controversially discussed – although their structures have been resolved with less unambiguity. Artificial molecular catalysts have been developed in the last years to obtain vital insights into the O-O bond formation step. This review put together the scarce literature on the topic that helped in understanding the key steps in the O-O bond formation reactions mediated by high-valent oxo complexes of the first-row transition metals.

Diiron macrocyclic complexes have been often considered as catalytically inert. However, numerous published examples of the catalytic oxidation reactions mediated by these complexes indicate their potential in catalysis. Mechanistic background for their applications as oxidation catalysts and their relationship with enzymatic and biomimetic oxidation involving cytochrome P-450 and soluble methane monooxygenase are discussed. A special emphasis was put on the N-bridged diiron phthalocyanine complexes as an emerging class of oxidation catalysts. Their unusual Fe(μN)Fe structure has interesting catalytic properties and reactivity. In addition to oxidation of strong C–H bonds in alkanes including methane, aromatic, and alkylaromatic compounds, μ-nitrido diiron phthalocyanines catalyze the oxidative dehalogenation and the formation of C–C bonds. A clean and practical character of the catalytic systems coupled with real availability of the phthalocyanines suggests a possibility of the application of this approach in industry. Great potential for further developments by modification of the catalysts structure can be envisioned.