126422-97-7Relevant academic research and scientific papers
Inter-Metal Nitrogen Atom Transfer Reactions between Nitridochromium(V) and Chromium (III) Porphyrins
Neely, Frank L.,Bottomley, Lawrence A.
, p. 5432 - 5434 (2008/10/09)
Reactions of nitridochromium(V) porphyrins with chromium(III) porphyrins resulted in reversible, inter-metal nitrogen atom transfer between the two chromium porphyrin complexes. The progress of these reactions was followed spectrophotometrically. Kinetic analysis of the spectral data obtained over time for a variety of substituted porphyrins showed the reactions to be first order in each of the reactants and second order overall. Equilibrium constants were computed from the spectral data and ranged from 0.56 to 2.1 for the reactions between nitridochromium(V) octaethylporphyrin and a series of chlorochromium(III) tetraphenylporphyrins possessing phenyl ring substituents. Forward rate constants were determined for this reaction series and ranged from 6.8 to 1420 M-11 s-1. Electron-withdrawing substituents enhanced the forward rates but diminished the equilibrium constants. It is proposed that the reactions proceed by nucleophilic attack of the nitridochromium porphyrin donor on the cationic chromium(III) porphyrin nitrogen atom acceptor facilitating a net, two-electron redox process mediated by a homobimetallic μ-nitrido intermediate.
Stereoelectronic Aspects of Inter-Metal Nitrogen Atom Transfer Reactions between Nitridomanganese(V) and Chromium(III) Porphyrins
Bottomley, Lawrence A.,Neely, Frank L.
, p. 5435 - 5439 (2008/10/09)
Reactions of nitridomanganese(V) porphyrins with chromium(III) porphyrins resulted in the irreversible formation of nitridochromium(V) porphyrins and manganese(III) porphyrins. The progress of these reactions has been followed spectrophotometrically, electrochemically, and spectroscopically by EPR. Kinetic analysis of the spectrophotometric data obtained during these reactions for a variety of substituted porphyrins showed the reactions to be first order in each of the reactants. Rate constants were dependent upon the electronic and steric effects of the porphyrin substituent, upon the identity of the anion bound to the chromium(III) reactant, and upon the solvent dielectric constant. We propose that the mechanism of these nitrogen atom transfer reactions involves the nucleophilic attack of the nitridomanganese porphyrin donor on the cationic chromium(III) porphyrin acceptor facilitating a net, two-electron redox process mediated by a heterobimetallic μ-nitrido intermediate. This report represents the first systematic study of the stereoelectronic effects involved in the complete, inter-metal nitrogen atom transfer between two metalloporphyrins.
