Access to the Bis-benzene Cobalt(I) Sandwich Cation and its Derivatives: Synthons for a "Naked" Cobalt(I) Source?

The synthesis and structural characterization of the hitherto unknown parent Co(bz) (bz=benzene) complex and several of its derivatives are described. Their synthesis starts either from a CoCO salt, or directly from Co (CO) and a Ag salt. Stability and solubility of these complexes was achieved by using the weakly coordinating anions (WCAs) [Al(OR ) ] and [F{Al(OR ) } ] {R =C(CF ) } and the solvent ortho-difluorobenzene (o-DFB).

From an Easily Accessible Pentacarbonylcobalt(I) Salt to Piano-Stool Cations [(arene)Co(CO) ].

The facile synthesis of a pentacarbonyl cobalt(I) salt without the need for a superacid as solvent is presented. This salt, [Co(CO) ] [Al(OR ) ] {R =C(CF ) }, readily accessible on a multigram scale, undergoes substitution reactions with arenes yielding the hitherto unknown class of two-legged cobalt piano-stool complexes [(arene)Co(CO) ] with four different arene ligands. Such a substitution chemistry would have been impossible in superacid solution, as the arenes used would have been oxidized and/or protonated.