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). The magnetic properties of Co(bz) were measured and compared in the condensed and gas phases. The weakly bound Co(o-dfb) salts are of particular interest for the preparation of further Co salts, for example, the structurally characterized low-coordinate 12 valence electron Co(P Bu ) and Co(NHC) salts.