Optically active organometallic compounds. Part I. Absolute configuration of (–)-1,1′-dimethylferrocene-3-carboxylic acid by X-ray analysis of its quinidine salt

Abstract

The quinidine salt of (–)-1,1′-dimethylferrocene-3-carboxylic acid crystallises from aqueous ethanol as a monohydrate: the crystals are orthorhombic, space group P2₁2₁2₁, with four units of C₃₃H₄₀FeN₂O₅ in a cell of dimensions a= 15·44, b= 28·12, c= 6·79 Å. The crystal structure was elucidated by the heavy-atom method, and Fourier and least-squares methods were employed in the determination of the atomic parameters. The analysis defines the absolute configuration of (–)-1,1′-dimethylferrocene-3-carboxylic acid and confirms the accepted absolute stereochemistry of the alkaloid quinidine. The molecules are held together in the crystal by a system of hydrogen bonds.