Electrochemical, Chemical, and Spectroscopic Characterization of the frans-[Tetracarbonylbis(triphenylphosphine)chromium]+/0 Redox Couple

R. N. Bagchi, A. M. Bond, G. Brain, T. L.E. Henderson, R. Colton, J. E. Kevekordes

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Abstract

Electrochemical oxidation of trans-Cr(CO)4(PPh3)2 at mercury, silver, or platinum electrodes or chemical oxidation with AgC1O4, NOPF6 or NOBF4 produces trans-[Cr(CO)4(PPh3)2]+. The 17-electron monomeric cation has been characterized by analysis and a wide variety of electrochemical (polarographic, voltammetric, and controlled potential electrolysis) and spectroscopic (infrared, electron spin resonance) techniques. trans-[Cr(CO)4(PPh3)2]+ is light and moisture sensitive and unlike trans-Cr(CO)4(PPh3)2 reacts relatively rapidly with acetonitrile, acetone, iodide, and bromide as well as water. All reactions studied produce trans-Cr(CO)4(PPh3)2 as a product, in some cases (bromide and iodide) by redox reactions and in others by disproportionation. Electron-transfer catalysis reactions initiated via the ligand, L, substitution reaction trans-[Cr(CO)4(PPh3)2]+ + L ⟶ trans-[Cr(CO)4PPh3L]+ + PPh3 do not appear to be favored, although the observation of Cr(CO)5PPh3 as a reaction product with CO in the presence of light suggests that this step may be light catalyzed. This reaction, if it occurs, is a slow step relative to other pathways, and the [Cr(CO)4(PPh3)2]+/0 redox couple is not a good candidate for electron-transfer catalysis.

Original languageEnglish
Pages (from-to)4-9
Number of pages6
JournalOrganometallics
Volume3
Issue number1
DOIs
Publication statusPublished - Mar 1984
Externally publishedYes

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