The case of a Cd2Cu2 complex containing an apparently C3-symmetric ligand: Erroneous ligand-structure assignment by X-ray diffraction data analysis

A simplified synthesis of a previously reported Cd2Cu2 complex 4 was developed in order to have a more readily available source of 1,3,5-tris(trifluoromethyl)-cyclohexane-cis,cis-1,3,5-triol 1, a unique tridentate ligand, only tentatively identified elsewhere. Attempts to liberate the ligand from 4 resulted in the sole formation of 2,4,6-tris(trifluoromethyl)-tetrahydropyran-cis,cis-2,4,6-triol (2); no traces of 1 were detected. A newly conducted X-ray analysis of complex 4 led to diffraction data that could be explained either by the previously reported structure for 4 or by the statistically disordered structure 5, containing ligand 2 rather than 1. Whereas refinement of both models led to equivalent merit factors, mass spectral data and elemental analysis of the crystals revealed unequivocally the sole presence of the tetrahydropyran derivative within the complex and proved thus the erroneous structure assignment 4 previously published for compound 5.

Previously reported complex 4 was resynthesized in order to have a more readily available source of cyclohexane 1. Attempts to liberate the ligand from 4 resulted in the sole formation of pyrane 2. This observation conflicts with X-ray analytical data, but could be resolved by synthetic and mass analytical results.Figure optionsDownload as PowerPoint slide