Rhenium complexes of tris(pyrazolyl)methanes and sulfonate derivative

Abstract

The trioxo [ReO₃{SO₃C(pz)₃}] (1) (pz = pyrazolyl) and oxo [ReOCl{SO₃C(pz)₃}(PPh₃)]Cl (2) compounds with tris(pyrazolyl)methanesulfonate were obtained by treatment of Re₂O₇ or [ReOCl₃(PPh₃)₂], respectively, with Li[SO₃C(pz)₃], whereas [ReCl₃{HC(pz)₃}] (3), [ReCl₃{HC(3,5-Me₂pz)₃}] (4) and [ReCl₄{η²-HC(pz)₃}] (5) were prepared by reaction of [ReOCl₃(PPh₃)₂] (3,4) or [ReCl₄(NCMe)₂] (5) with hydrotris(pyrazolyl)methane HC(pz)₃ (3,5) or hydrotris(3,5-dimethyl-1-pyrazolyl)methane HC(3,5-Me₂pz)₃ (4). [ReO{SO₃C(pz)₃}{OC(CH₃)₂pz}][ReO₄] 6, with a chelated pyrazolyl-alkoxide, was derived from an unprecedented ketone-pyrazolyl coupling on reaction of crude 1 with acetone. The compounds have been characterized by elemental analyses, IR and NMR spectroscopies, FAB-MS spectrometry and cyclic voltammetry and, in the case of 5 and 6, also by single-crystal X-ray diffraction. The electrochemical E_L Lever parameter has been estimated, for the first time, for the SO₃C(pz)₃⁻ and oxo ligands allowing the measurement of their electron-donor character and comparison with other ligands. Compounds 1, 2 and 6 appear to be the first tris(pyrazolyl)methanesulfonate complexes of rhenium to be reported.