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I. OXIDATIVE ELECTROCHEMICAL STUDIES OF ARENEBIS(TRICARBONYLCHROMIUM) COMPOUNDS. II. ELECTROCHEMICAL AND EPR STUDIES OF NEW ORGANIC ELECTRON ACCEPTORS. III. REDUCTIVE ELECTROCHEMICAL STUDIES OF ARENEBIS(TRICARBONYLCHROMIUM) COMPLEXES
Abstract
Arenetricarbonylchromium complexes of the type (CH(,3))(,2)E{C(,6)H(,5)Cr(CO)(,3)}(,2), where E = C, Si, Ge, Sn, Pb, and (CH(,3))(,2)Sn{ArCr(CO)(,3)}(,2), where Ar = phenyl or substituted phenyl, yield dications upon electrochemical oxidation which, with judicious use of solvent media, are persistent on the cyclic voltammetric time scale. The individual arenetricarbonylchromium moieties of these compounds are shown by their electrochemical characteristics to be noninteracting and to adhere to the Bard-Anson-Saveant model. The persistence is shown to be due to steric bulk around the phenyl rings. Removal of the insulating (CH(,3))(,2)E group allows for interaction between the pi bound arene rings. Mixed-valence character is indicated but such cations are much less persistent. Bis(tricarbonylchromium) complexes of biphenyl, 9,10-dihydrophenanthrene and cis- and trans-stilbene reduce electrochemically to form very long-lived dianions. These complexes form a new class of arenetricarbonylchromium compounds in that they reduce in a one electron per chromium fashion. This contrasts with phenyl- and naphthylcomplexes which reduce with two electrons per chromium atom. Studies indicate that the chromium atoms are in the -1 oxidation state. A mechanism of the ECE type for the electrochemical reduction process is proposed. Several other arenetricarbonylchromium compounds were investigated by electrochemical techniques in a preliminary manner. A number of substituted acenaphthylene and acenaphthene compounds were investigated by electrochemical and EPR techniques in a search for possible new organic electron acceptors. New electrophores tested in this way include the 1,2-dicyanoethylene, maleic anhydride, peri-cyano and peri-nitro moieties. Each of these groups are excellent electron sinks and EPR investigations provided insight into the spin distribution of the radical anions formed. 1,2,5,6-Tetracyanoacenaphthylene was found to be reduced almost as easily as TCNQ. 1,2-Dibromo-5,6-dinitroacenaphthylene exhibits a difference between the first and second reduction waves which is smaller than TCNQ. Production here of the radical anions of 1,2-dibromo-5,6-dinitroacenaphthylene and of 1,2-dibromo-5,6-dicyanoacenaphthylene appear to be the first reports ever of persistent radical anions of aryl bromides.
Subject Area
Organic chemistry
Recommended Citation
MILLIGAN, STUART NEIL, "I. OXIDATIVE ELECTROCHEMICAL STUDIES OF ARENEBIS(TRICARBONYLCHROMIUM) COMPOUNDS. II. ELECTROCHEMICAL AND EPR STUDIES OF NEW ORGANIC ELECTRON ACCEPTORS. III. REDUCTIVE ELECTROCHEMICAL STUDIES OF ARENEBIS(TRICARBONYLCHROMIUM) COMPLEXES" (1982). ETD collection for University of Nebraska-Lincoln. AAI8302107.
https://digitalcommons.unl.edu/dissertations/AAI8302107