Synthesis and structural characterization of dinuclear complexes of trivalent aluminum, gallium, indium and chromium derived from pyrazole-2-ethanol

The reaction of 1-(2-hydroxyethyl)-3,5-dimethylpyrazole (HL) with anhydrous metal(III) halides (M = Al, Ga, In and Cr) results in the isolation of four novel dinuclear complexes [Al(μ-L)Cl2]2 (1), [Ga(μ-L)Cl2]2 (2), [In(μ-L)Br2(H2O)]2·2thf (3) and [Cr(μ-L)Cl2(H2O)]2·1.5thf (4) in good yields. The new complexes have been characterized with the aid of analytical and spectroscopic studies. A single crystal X-ray structure determination in each case confirms the dimeric structure for all the complexes in the solid-state. The pyrazole ethanol ligand binds to the metal through both pyrazole nitrogen and bridging alkoxide oxygen terminals with the formation of a central M2O2 core involving the ethoxide anion. The metal(III) center is pentacoordinated in compounds 1 and 2, while it is hexacoordinated in compounds 3 and 4.

The synthesis and characterization of the Al(III), Ga(III), In(III) and Cr(III) pyrazole ethanolate complexes are reported. The new compounds have been characterized by elemental analysis, FT-IR, 1H NMR and TG/DTA analysis. A single crystal X-ray structure determination in each case confirmed the molecular structure in the solid-state.Figure optionsDownload as PowerPoint slideHighlights
► Novel dimeric alkoxo group 13 and chromium halides have been synthesized.
► All new complexes have been characterized by single crystal X-ray diffraction.
► Compounds 2 and 3 form supramolecular motifs aided by strong hydrogen bonds.