Dicobalt hexacarbonyl derivatives of chiral acetylenes

(μ₂-RC₂R′)Co₂(CO)₆ complexes are prepared where R ≠ R′ and one of these substituents is a chiral organic group. The structures of the 11 complexes (10 new) range from the simplest possible chiral acetylenic hydrocarbon derivative (S-3-methyl-1-pentyne 1a) to ethynylsteroid (1f, 1g, 1h) and ethynylcodeine (1i, 1j, 1k) derivatives. The CD spectra are reported and the results are analysed in terms of a quadrant rule. The CD spectra show that in all complexes the Co₂(CO)₆ fragment of the molecule gets chirally perturbed. The reasons for the chiral perturbation include apolar repulsing (dominant for the hydrocarbon acetylenes) and polar attractive ("autosolvation"; dominant for acetylenes with polar hetero-atom containing substituents) forces. © 1995.