Rhenium complexes of tris(pyrazolyl) methanes and sulfonate derivative

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-Me(2)pz) (3)}] (4) and [ReCl4{eta(2)-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-Me(2)pz)(3) ( 4). [ReO{SO3C(pz)(3)}{OC(CH3)(2)pz}][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.