Syntheses and properties of Re(III) complexes derived from hydrotris(1-pyrazolyl)methanes: molecular structure of [ReCl2(HCpz3)(PPh3)][BF4]

The complexes [ReCl2{N2C(O)Ph}(Hpz)(PPh3)2] (1) (Hpz = pyrazole), [ReCl2{N2C(O)Ph}(Hpz)2(PPh3)] (2), [ReCl2(HCpz3)(PPh3)][BF4] (3) and [ReCl2(3,5-Me2Hpz)3(PPh3)]Cl (4) were obtained by treatment of the chelate [ReCl2{η2-N,O–N2C(O)Ph}(PPh3)2] (0) with hydrotris(1-pyrazolyl)methane HCpz3 (1,3), pyrazole Hpz (1,2), hydrotris(3,5-dimethyl-1-pyrazolyl)methane HC(3,5-Me2pz)3 (4) or dimethylpyrazole 3,5-Me2Hpz (4). Rupture of a C(sp3)–N bond in HCpz3 or HC(3,5-Me2pz)3, promoted by the Re centre, has occurred in the formation of 1 or 4, respectively. All compounds have been characterized by elemental analyses, IR and NMR spectroscopy, FAB-MS spectrometry, cyclic voltammetry and, for 1 · CH2Cl2 and 3, also by single crystal X-ray analysis. The electrochemical EL Lever parameter has been estimated, for the first time, for the HCpz3 and the benzoyldiazenide NNC(O)Ph ligands.