Synthesis and characterization of divalent metal complexes containing the heteroscorpionate ligand dihydrobis(3-carboxyethyl-5-methylpyrazolyl)borate

The dihydrobis(3-carboxyethyl-5-methylpyrazolyl)borate ligand, Bp^COOET,Me, reacts with divalent metals to yield complexes of general type (Bp^COOET,Me)₂M], where M = Mn(II), Fe(II), Co(II), Ni(II), Zn(II), Cu(II), Pb(II) and Cd(II). All complexes have been fully characterized by elemental analyses and FT-IR in the solid state and by NMR (¹H and ¹¹³Cd NMR) spectroscopy and electrospray ionization mass spectrometry in solution. A single crystal structural characterization is reported for Cu(Bp^COOET,Me)₂] and Zn(Bp^COOET,Me)₂]. In the two complexes, both metals are four-coordinated and they are only bound to the nitrogen atoms of the bis(pyrazolyl)borate ligand; however, while the environment of the copper atom is square planar, that of the zinc center shows a tetrahedral distorted conformation.