An investigation of the electronic structures of CpCo(CO)(2) and CpCo(CO)(2)(-) using experimental and theoretical techniques

An upper bound for the adiabatic electron affinity of cyclopentadienylcobaltdicarbonyl [CpCo(CO)(2)] is 0.86 +/- 0.2 eV as determined by fixed-frequency negative-ion photoelectron spectroscopy. During the course of the experimental work, the generation of the binuclear complex [CpCo(CO)(2)](2)(-) is detected, and, to our knowledge, this is the first observation of this anionic cluster. Electronic structural calculations using both the density functional theory formalism and ab initio techniques are completed for both CpCo(CO)(2) and the corresponding negative-ion. A DFT/DZVP2 calculation yields the vertical electron affinity of CpCo(CO)(2) as 0.84 +/- 1.0 eV, The theoretical results confirm that a weak ''allyl-ene'' type structure exists in the cyclopentadienyl ligand of both molecules, but the distortion is less pronounced in CpCo(CO)(2)(-) than in CpCo(CO)(2). Our results lend further support to the classification of CpCo(CO)(2)(-) as a 19-electron complex.