Rhenium Tris(pyrazolyl)borate Complexes with O-Donor Ligands: Synthesis and Structures

The reaction of TpReOCl(2) (Tp is the tris(pyrazolyl)borate anion) with methanol in the presence of triethylamine affords new rhenium alkoxide complex TpReO(OMe)(2) (I). Unlike the starting complex resistant to hydrolysis, complex I reacts with water in toluene to form the dimeric complex [TpReO(mu-O)](2) (II). The action of a large amount of water in acetone also leads to the decomposition of some Tp ligands and formation of the cationic complex [(TpReO)(2)(mu-O)(mu-C3H3N2)]ReO4 (III) with the pyrazolate bridging ligand and perrhenate anion on the external sphere. The treatment of complex I with acetic anhydride gives the rhenium tris(pyrazolyl)borate complex bearing terminal acetate substituents TpReO(OAc)(2) (IV). The synthesized complexes are characterized by IR and NMR spectroscopy, and their structures are determined by X-ray diffraction (CIF files CCDC nos. 2081834 (I), 2081835 (II), 2081836 (III), 2081837 (IV)).