Tartrate-Derived Cyclopentadienes for the Synthesis of Chiral Substituted (η5-Cyclopentadiene)(η4-cycloocta-1,5-diene)cobalt(I) Complexes

Two chiral tartrate-derived ligands, the disubstituted cyclopentadiene 1 and the new tetrasubstituted cyclopentadiene 2, are obtained. The corresponding ( η 5 -cyclopentadiene)( η 4 -cycloocta-1,5-diene)cobalt(I) complexes 3 and 4 are prepared through the deprotonation of the ligands with lithium diisopropylamide followed by the metathetic reaction of the lithium salts with tris(triphenylphosphine)cobalt(I) chloride and 1,5-cyclooctadiene. The complexes are isolated in an enantiomerically pure state after chromatography with dried silica under argon. The structures of 2 − 4 have been determined by single-crystal X-ray diffractometry. The dynamic behavior of complexes 3 and 4 in solution is discussed on the basis of 1 H and 13 C NMR spectra.