1,2,4,5-Tetrazine: Synthesis and Reactivity in [4+2] Cycloadditions

Carbonyl and olefin adducts of coinage metals supported by poly(pyrazolyl)borate and poly(pyrazolyl)alkane ligands and silver mediated atom transfer reactions.

A detailed kinetic and mechanistic analysis of the classical “brown-ring” reaction of [Fe(H2O)6]2+ with NO was performed using stopped-flow and laser flash photolysis techniques at ambient and high pressure. The kinetic parameters for the “on” and “off” reactions at 25 °C were found to be kon = 1.42 × 106 M-1 s-1, ΔH⧧on = 37.1 ± 0.5 kJ mol-1, ΔS⧧on = −3 ± 2 J K-1 mol-1, ΔV⧧on = +6.1 ± 0.4 cm3 mol-1, and koff = 3240 ± 750 s-1, ΔH⧧off = 48.4 ± 1.4 kJ mol-1, ΔS⧧off = −15 ± 5 J K-1 mol-1, ΔV⧧off = +1.3 ± 0.2 cm3 mol-1. These parameters suggest that both reactions follow an interchange dissociative (Id) ligand substitution mechanism, which correlates well with the suggested mechanism for the water exchange reaction on [Fe(H2O)6]2+. In addition, Mossbauer spectroscopy and EPR measurements were performed on the reaction product [Fe(H2O)5(NO)]2+. The Mossbauer and EPR parameters closely resemble those of the {FeNO}7 units in any of the other well-characterized nitrosyl complexes. It is concluded that its electron...

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Kinetics, mechanism, and spectroscopy of the reversible binding of nitric oxide to aquated iron(II). An undergraduate text book reaction revisited.

The reduction of nitrite to nitric oxide in dissimilatory denitrification is carried out by copper nitrite reductases (CuNIRs) via a type 2 copper site. Extended studies on CuNIRs in combination with model complexes have allowed for the establishment of two potential mechanisms for this transformation. Recent experimental and computational results have revealed further details of this process. In addition, the interaction of NO with copper sites has recently gained much attention. This review discusses recent results in the context of the known coordination chemistry of CuNIRs.

Binding and activation of nitrite and nitric oxide by copper nitrite reductase and corresponding model complexes

Publisher Summary This chapter provides a critical review of the preparation, characterization (which is often incomplete), and properties of cyanide complexes of the transition metals. It focuses on structural, thermodynamic, and kinetic data. Two prominent features of transition metal cyanide chemistry are the wide range of metal:ligand ratios in complexes and the existence of many metals in low oxidation states. The chapter discusses the bearing of the physical state of metal cyanides on structural investigations. There are two important consequences of the fact that cyanide is an ion and not a neutral molecule: metal cyanides and their complexes are nonvolatile salts rather than volatile molecular entities and much of their chemistry is concerned with processes and measurements in solution in solvents of high complexing power, so that differences in complexing by solvent and ligand are involved. The chapter considers the effect of cyanide on the stabilities with respect to oxidation and reduction of metal ions in aqueous media, taking Fe(II) and Fe(III) as an example.

W. Manchot

Papers

Ueber Derivate des Triazols

Über Kohlenoxyd bindende Eisensalze

Zur Kenntnis der Körper mit dreifacher Bindung

Ueber die Cuproverbindungen des Kohlenoxydes

Ueber die Ferroverbindungen des Stickoxyds. [Zweite Mittheilung.]