We report the isolation, characterization, and reactions of the unsaturated complex (LCo)-Co-tBu (L-tBu = bulky beta-diketiminate ligand). The unusual slipped kappa N,eta(6)-arene binding mode in (LCo)-Co-tBu interconverts rapidly and reversibly with the traditional kappa N-2,N' ligation mode upon binding of Lewis bases, making it a "masked" two-coordinate complex. The mechanism of this isomerization is demonstrated using kinetic studies. (LCo)-Co-tBu is a stable yet reactive synthon for low-coordinate cobalt(I) complexes and is capable of cleaving the C-F bond in fluorobenzene.