LIGAND-MEDIATED METAL-METAL INTERACTIONS IN (ETA(5)ETA(5)-FULVALENE)BIS(DICARBONYLCOBALT) AND RHODIUM COMPLEXES

Gas phase photoelectron spectroscopy (PES) is used to investigate the bonding and electronic structure in (fv) [M(CO)(2)](2) (fv=fulvalene, eta(5):eta(5)-C10H82-;M=CO,Rh). The results for these bimetallic compl exes are also compared to those for the analogous monometallic complex es CpM(CO)(2) (Cp=eta(5)-C5H5-; M=Co, Rh) which have been reported pre viously. The low valence ionization patterns observed for CpCo(CO)(2) and (fv)[Co(CO)(2)](2) are very similar, indicating that there is litt le electronic interaction between the two metals of the dicobalt compl ex. The spectrum of (fv)[Rh(CO)(2)](2) also is very similar to the spe ctrum of CpRh(CO)(2), except that the first metal ionizations in the b imetallic rhodium compound show a significant splitting (0.45 eV). Thi s splitting is due to electronic interaction between the two metal cen ters which occurs via communication through the fulvalene pi system. T he differences in electronic structure are compared to the differences in electrochemical behavior of the Co and Rh fulvalene complexes.