Speciation of Bulky Chiral Cyclopentadienyl Cobalt(III) Complexes: Isolation of Air-Stable 16-Electron Species

Bulky pentasubstituted chiral cyclopentadienyl ligands (Cp V ) were shown to form distinct species upon cobalt(III) complexation, which differ in the nature and number of auxiliary ligands. Aside from the well-established coordinatively saturated Cp V Co(CO)I 2 architecture and its dimeric [Cp V CoI 2 ] 2 derivative, the formation of monomeric 16-electron species of type Cp V CoI 2 was confirmed as well, thus representing a rare example of air-stable chiral half-sandwich complexes with an unsaturated 3d-metal center. Herein, we report the isolation and structural characterization of these organometallic species, of which the dominant coordination mode depends on the steric encumbrance of the employed Cp V ligand. Addition of a two-electron donor ligand, such as carbon monoxide or an isocyanide, showed that the unsaturated complexes can be converted back to 18-electron adducts.