I. A STUDY OF THE REDUCTIVE CHEMISTRY OF NAPHTHALENETRICARBONYLCHROMIUM. II. OTHER EXPLORATORY ELECTROCHEMICAL STUDIES

In light of previous electrochemical results that demonstrated that (eta)(\u276)-naphthalenetricarbonylchromium could be reduced by two-electrons to form a stable dianion, a study of the dianion thus formed was undertaken. This investigation included the spectro- scopic characterization of the dianion by (\u271)H NMR, (\u2713)C NMR, and IR spectroscopy. From this data, it was postulated that the dianion was an (eta)(\u274)-napthalenetricarbonylchromium complex, which, upon reduction had isomerized via a slip-fold mechanism. If this spe- cies was allowed to react with a proton source, the product was (eta)(\u275)-cyclohexadienyltricarbonylchromium anion in which protona- tion had occurred at the 1 position of the naphthalene ring in an endo fashion presumably via the intermediacy of a metal hydride. Addition of an alkyl halide to a solution of the dianion resulted in the decomplexation of the naphthalene ring. (eta)(\u276)-benzenedicarbonylthiocarbonylchromium and (eta)(\u276)-toluene- dicarbonylthiocarbonylchromium were synthesized by known methods. The reductive electrochemistry of these complexes was investigated and compared with that of the corresponding tricarbonyl derivatives. In both instances, the thiocarbonyl deriv- ative reduced appreciably anodic of the parent. Also, the species formed upon reduction was more stable with a thiocarbonyl ligand. These results are rationalized in terms of the increased electron withdrawing ability of the thiocarbonyl ligand when compared with the carbonyl ligand. Likewise, an electrochemical study of pentacarbonylthiocarbonyl- chromium and hexacarbonylchromium was undertaken. Similar to the results obtained for the arene study above, it was found that the thiocarbonyl derivative reduced easier than the parent hexacarbonyl. However, the primary reduction product decomposed faster for the thiocarbonyl. The likely mechanism for this decomposition is carbon monoxide loss from the radical anion