Tris-phenyl substituted tris(pyrazolyl)methane: Victim of a novel rearrangement in a cobalt(II) complex

The bisfacial cobalt(II) complex [(HC(3-Phpz)2(5-Phpz))2Co][BF4]2 (1) was prepared by reaction of the tris(pyrazolyl)methane HC(3-Phpz)3 with Co(BF4)2·6H2O. A remarkable ligand rearrangement reaction occurs resulting in incorporation of the new ligand HC(3-Phpz)2(5-Phpz). Complex 1 was characterised by X-ray crystallography, mass spectrometry, IR spectroscopy and elemental analysis. DFT studies on both ligands as well as on complex 1 complement the experimental investigation.