The Crystal and Molecular Structure of rac‐15‐cyano‐1,2,2,7,7,12,12‐heptamethyl corrin hydrochloride, metal free corrin

The crystal structure of a metal free corrin hydrochloride synthesised by Eschenmoser & Fischli has been found by X-ray analysis. The crystals are monoclinic and contain ethanol of crystallisation; a = 10.84 A, b = 12.04 A, c = 26.04 A, γ = 120.4 in space group P21/a. The structure was determined by direct methods and refined to R = 0.076 for 3252 statistically significant reflections with θ < 70° (Cu Kα). The A ring is found to be markedly displaced from the mean plane of the other three rings; hydrogen atoms are observed in difference electron density maps to be bonded to N21 and N23 of the nucleus. Details of the shape and dimensions of the nucleus are discussed.