Resolution of the [6,6′-μ-(CH 3) 2P-(1,7-(C 2B 9H 10) 2)-2-Co] bridged cobaltacarborane to enantiomers pure by chiral HPLC, circular dichroism spectra and absolute configurations by X-ray diffraction

Abstract

Racemic [6,6′-μ-(CH 3) 2P-(1,7-(C 2B 9H 10) 2)-2-Co] zwitterion 1R was resolved into enantiomers 1A and 1B by chiral HPLC, and, for the first time for a chiral metallacarborane, absolute configurations of both enantiomers were determined by X-ray diffraction. HPLC results, circular dichroism spectra and crystallographic data [orthorhombic, space group P2 12 12, Z=8; 1A: a=11.5180(5) Å, b=12.4741(6) Å, c=13.8335(8) Å, V=1987.6(2) Å 3, 1B: a=11.5177(3) Å, b=12.4700 Å, c=13.8326(6) Å, V=1986.7(1) Å 3] are presented. Nomenclature and correlation of the CD curves with those reported earlier for closely related analogs, are discussed, along with general implications for chiral HPLC resolutions on a β-cyclodextrin column.