Chemical behavior of ortho-hydroquinone-based bis(pyrazol-1-yl)methane ligands in the presence of palladium(II) chloride

The synthesis, structural characterization, and coordination behavior of ditopic ortho-hydroquinone-based bis(pyrazol-1-yl)methane ligands (ortho-(OH)2C6H3-4-CHpz2, ortho-(OH)2C6H3-4-CH(3-Phpz)2, and ortho-(OH)2C6H3-4-CH(3-tBupz)2) with pyrazole, 3-phenylpyrazole, and 3-tert-butylpyrazole as donors are described. The reaction of a soluble PdCl2-source with ortho-(OH)2C6H3-4-CHpz2 in acetonitrile yielded the related square-planar N,N-coordinated Pd(II) dichloride complex, whereas treatment of ortho-(OH)2C6H3-4-CH(3-Phpz)2 or ortho-(OH)2C6H3-4-CH(3-tBupz)2 with PdCl2 in acetonitrile resulted in degradation of these ligands. The Pd(II) complexes trans-(3-PhpzH)2PdCl2 and trans-(3-tBupzH)2PdCl2 were isolated and fully characterized including X-ray diffraction analyses.