The electrochemistry of several ruthenium porphyrin nitrosyl chloride complexes [Ru(por)(NO)Cl] have been examined in tetrahydrofuran (THF). The complexes undergo one‐electron irreversible reductions, which result in diffusion‐limited substitutions of the chloride ligands for THF. This chloride metathesis is reversible in the presence of added NBu4Cl, and equilibrium constants and rate constants for chloride loss have been estimated. These parameters correlate with the NO stretching frequencies of the parent complexes, with more electron‐donating porphyrin ligands favoring chloride loss from the reduced complexes. The [Ru(por)(NO)(THF)] products of the reductions can be detected by IR, EPR, and visible spectroscopies. These species undergo three further reductions, with good reversibility at scan rates >0.40 V s−1. The [Ru(por) (NO)(THF)]+/0 couples have also been determined, and the rate constants and equilibrium constants for recombination with chloride have been estimated. One‐electron reductions of the [Ru(por)(NO)Cl] complexes result in approximately 1018 enhancement of the rates of chloride loss.
The Front Cover shows cartoons of species formed during cyclic voltammetry (CV) analysis of [Ru(porphyrin)(NO)Cl] in tetrahydrofuran. The initial redox‐induced reversible solvent‐for‐chloride metathesis shown in the reaction at the top occurs at diffusion‐limited rates. This reaction, and others, were elucidated by analysis and simulation of CV data, chemical reduction, and IR spectroelectrochemistry. Subsequent electron‐transfer reactions occur at the thus‐formed solvento species, which features a bent NO ligand. More information can be found in the Article by J. R. Zink et al. on page 861 in Issue 6, 2018 (DOI: 10.1002/celc.201701001).
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