Cationic Sandwich Complexes of Cobalt(I): The Parent Bis-benzene Cobalt(I) Complex and Access to its Weakly Bound Homologues - Synthons for a "Naked" Cobalt(I) Source…?

The synthesis and structural characterization of the hitherto unknown parent Co(bz)(2)(+) (bz = benzene) complex and several of its derivatives are described. Their synthesis starts either from a CoCO5+ salt, or directly from Co-2(CO)(8) and a Ag+ salt. Stability and solubility of these complexes was achieved by using the weakly coordinating anions (WCAs) [Al(ORF)(4)](-) and [F{Al(ORF)(3)}(2)](-) {R-F=C(CF3)(3)} and the solvent ortho-difluorobenzene (o-DFB). The magnetic properties of Co(bz)(2)(+) were measured and compared in the condensed and gas phases. The weakly bound Co(o-dfb)(2)(+) salts are of particular interest for the preparation of further Co-I salts, for example, the structurally characterized low-coordinate 12 valence electron Co((PBu3)-Bu-t)(2)(+) and Co(NHC)(2)(+) salts.