Solvent-dependent assembly of discrete and continuous CoCl₂ adamantane-based ligand complexes: observations by CSI-mass spectrometry and X-ray crystallography.

Discrete and continuous coordination structures were obtained in single crystals of CoCl₂ and an adamantane-based bidentate ligand bearing imidazolyl groups, depending on the methanol concentration in a methanol-chloroform mixture. Single-crystal X-ray structure analysis revealed that the metal centers exhibited a tetrahedral geometry in the discrete complex and an octahedral geometry in the continuous metal complex. Conventional analytical methods, including UV-vis and NMR spectroscopy, could not identify those two complexes in solution. In contrast, cold-spray ionization mass spectrometry could detect differences between the discrete complex and the continuous metal complex, and ion peaks due to continuous ligand adducts were found only in the spectrum of the continuous metal complex.