Selective Synthesis of Heteroleptic Metal Complexes with Tris(pyrazolyl)methanes

The reaction of tris(3,5-dimethyl-1H-pyrazol-1-yl)methane (LMe) and cobalt(II) perchlorate affords new complex [Co(LMe)(CH3CN)3](ClO4)2, the structure of which is confirmed by X-ray diffraction (XRD) (CIF file CCDC no. 2405592). According to an analysis of the steric topographic map constructed on the basis of the XRD data, the stability of the synthesized complex is due to the presence in ligand LMe of the methyl group in position 3 of the pyrazole ring. The subsequent substitution of the solvent molecules in the internal coordination sphere of the cobalt(II) ion by tris(pyrazol-1-yl)methane (LН) gives heteroleptic complex [Co(LH)(LMe)](ClO4)2, which is characterized by NMR spectroscopy and mass spectrometry. A similar approach with the stage-by-stage introduction of the ligands into the coordination sphere of the metal ion with the formation of an intermediate 1 : 1 complex can be extended to other tripodal ligands, such as tris(triazolyl)- and tris(pyridyl)methanes or tris(triazolyl)- and tris(pyridyl)borates.