A sterically hindered tetrakis(pyrazolyl)borate: Synthesis, characterization and coordinative behaviour

Synthesis, structural and spectroscopic characterization and biomimetic properties of new copper, manganese, zinc complexes: Identification of possible superoxide-dismutase mimics bearing hydroxyl radical generating/scavenging abilities

“…The copper(II) chloro complex 4 was obtained from the reaction of two equivalents of K[Tp Ph,Me ] with one equivalent of the copper salt in methanol and in dichloromethane, respectively, at room temperature and in good yields (Scheme 3). The presence of the neutral Hpz Ph,Me coordinated to copper, is due to the hydrolysis of excess Tp Ph,Me , a phenomenon already observed [50]. The Mn complex [Mn(L 3 ) 2 ]·2H 2 O 5 was obtained from the reaction of two equivalents of the ligands HL 3 in MeOH with one equivalent of the metal salt (Scheme 3).…”

“…1630-1670 cm −1 , whereas uncoordinated carboxylate groups are generally observed at higher frequencies, above 1700 cm −1 [39,50].…”

Synthesis of Known and Previously Inaccessible Poly(pyrazolyl)Borates under Mild Conditions

“…Standard conditions were applied to the synthesis of Tkp x ligands increasing pyrazole and base amounts to almost stoichiometric 4.1 equiv to ensure complete conversion of BCl 3 ·SMe 2 into the desired tetrakis­(pyrazolyl)­borate. The scarce examples described of these ligands are almost restricted to those presenting methyl or hydrogen groups on positions 3 and/or 5 of the pyrazole rings due to the difficulty associated with the thermal introduction of the fourth heterocycle. ,,, Table shows the remarkable yields obtained for a variety of Tkp x Na ( 4a – f Na ) with highly encumbering substituents. Alkaline salts of these ligands are a common entrance to other metal complexes through metal exchange …”

Zinc, cadmium and mercury

“…Sterically demanding derivatives of tris(pyrazolyl)hydroborates reported with 3,3,3-and 3,3,5-(mes) 3 substitution patterns coordinate to zinc in a tridentate fashion, 12 also observed for the tetrakis(3-{p-tolyl}pyrazolyl)borate ligand. 13 The presence of additional neutral O-donor functionalities did not perturb the tridentate coordination mode with tris(3-{2-methoxy-1,1'dimethyl}pyrazolyl)hydroborate, 14 in contrast to the Mg compound in which all three methoxy groups were coordinated to a distorted octahedral magnesium cation. Heteroscorpionate ligands are also widely employed in the chemistry of zinc.…”