Crystallographic and theoretical study of the atypical distorted octahedral geometry of the metal chromophore of zinc(II) bis((1R,2R)-1,2-diaminocyclohexane) dinitrate

Comment on ”Crystallographic and theoretical study of the atypical distorted octahedral geometry of the metal chromophore of zinc(II) bis((1R,2R)-1,2-diaminocyclohexane) dinitrate”

“…The title compound in [1] was synthesized with the enantiopure ligand (1R,2R)-1,2-diaminocyclohexane and the stereochemistry is highlighted in the title of the article. Surprisingly, the crystal structure was solved and refined in the centrosymmetric space group P 2 1 /n with the zinc atom on an inversion center.…”

“…Six of the 14 non-hydrogen atoms have a non-positive definite displacement tensor. The Experimental Section of [1] mentions a thermal motion analysis with the THMA software [2]. The results are not provided but we assume that the program will fail, here.…”

“…Despite the wrong space group assignment, the unphysical atomic displacement parameters, the two missing hydrogen atoms (i.e. charged unit cell content), the low resolution of θ max = 24.93 • (d max = 0.84 Å), the low data completeness of 37.4% and the non-cryo measurement at T = 300K, the authors in [1] performed an extensive analysis based on the electron density from a multipole refinement. The experimental conditions for such a refinement have clearly…”

“…Figure 1: Displacement ellipsoid plot (50% probability level) created from the data in [1] (deposition number 1576255 in the Cambridge Structural Database [3]). The structure is based on a wrong space group assignment P 2 1 /n, and the zinc atom is erroneously constrained on an inversion center.…”

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We comment on the crystal structure of an enanantipure chiral zinc complex which has been described by Ivanova & Spiteller (2022) erroneously in a centrosymmetric space group with the metal on an inversion center. Subsequent information about thermal motion, octahedral distortion and charge density in their article is highly flawed.

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