PARAMAGNETIC ORGANOMETALLIC MOLECULES .5. TRICOBALT-CARBON LEWIS BASE DERIVATIVES

A detailed study of the redox behavior of Lewis base derivatives of tricobalt-carbon clusters, YCCo3(CO)9-nLn (n=1-3; L=R3P, (RO)3P, RNC), using the techniques of dc polarography at mercury electrodes and dc cyclic voltammetry at mercury or platinum, revealed that an electron-transfer series consisting of YCCo3(CO)9-nLn+/0/- does exist providing the right ligands are used. Monosubstituted derivatives undergo chemically reversible one-electron reduction at platinum or mercury electrodes in dichloromethane and acetone at 203 K. Reduction becomes progressively more difficult and oxidation easier as CO groups are replaced by Lewis bases. Thus, irreversible oxidations are seen when n=2, but when n=3, the derivatives show both reversible reduction and oxidation at platinum and mercury electrodes. Attempts to obtain the isotropic ESR spectra of the radical anions were thwarted by facile ligand dissociation, coupled with decomposition, such that only spectra of the YCCo3(CO)9-· species were observed. Frozen-solution spectra were obtained and these show that the a2 antibonding orbital of the Co3C clusters is only slightly perturbed by substitution of a CO group by a Lewis base. The electrochemical and ESR data are related to the electronic structure of these clusters. © 1979, American Chemical Society. All rights reserved.