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

Abstract

Abstract

High Resolution Image Download MS PowerPoint Slide Bulky pentasubstituted chiral cyclopentadienyl ligands (Cp V ) were shown to form distinct species, that differ in the nature and number of auxiliary ligands, upon classical cobalt(III) complexation with Co 2 (CO) 8 and I 2 . Aside from the expected and well-established coordinatively saturated Cp V Co(CO)I 2 architecture and its dimeric [Cp V CoI 2 ] 2 derivative, the unexpected 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. All three types of Cp V Co(III) speciation were analyzed by X-ray crystallography. 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.