Biogeochemistry can be defined as the mutual interactions (two-way) between the biology and chemistry of the Earth system, and as such is clearly an important component of the broader discipline of geobiology. It is a well-developed field, having a dedicated journal and textbook, and many hundreds of publications appearing in the scientific literature each year. Perhaps the best example of biogeochemistry is the balance between photosynthesis and respiration, autotrophy and heterotrophy, on Earth, the so-called Redfield equation. The modern practice of biogeochemical research has been focused on present-day processes such as those in the Redfield equation, but new tools and approaches are beginning to explore the biogeochemistry of the ancient Earth; this is the challenge for biogeochemists in the future.
Treatment of [RuHCl(CS)(PPh3)3] with Hg(o-C6H4NNC6H5)2 affords [RuCl(CS)(η2C,N-o-C6H4NNC6H5)(PPh3)2] (1) in good yield, where the cyclometallated azobenzene ligand coordinates through an ortho-C and one azo-N to give a five-membered chelate ring. Reaction of 1 with AgNO3 followed by NaBr Nike Blazer Achat or NaI affords the chloride-exchanged products [RuX(CO)(η2C,N-o-C6H4NNC6H5)(PPh3)2] (2, 3), whereas reaction of 1 with AgOC(O)Me Chaussure Nike Blazer Basse or NaS2CNEt2·2H2O gives the halide mono-phosphine-substituted complexes [Ru(CS)(LL)(η2C,N-o-C6H4NNC6H5)(PPh3)] (4, 5). In the solid-state structures of 1 and 3 there are significant changes in the bond lengths for the cyclometallated azobenzene ligand are observed relative to free azobenzene. These are discussed, Blazer Nike Homme Solde with the aid of spectroscopic and crystallographic data, in terms of a cis-push–pull effect.
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