Five-coordinate nickel(ii) complexes with carboxylate anions and derivatives of 1,5,9-triazacyclododec-1-ene: structural and 1H NMR spectroscopic studies

Abstract

The hydroxo complexes [Ni₂(mcN₃)₂(µ-OH)₂]₂(PF₆)₂ [mcN₃ = 2,4,4-trimethyl-1,5,9-triazacyclododec-1-ene (Me₃-mcN₃) or 2,4,4,9-tetramethyl-1,5,9-triazacyclododec-1-ene (Me₄-mcN₃)] react with the corresponding carboxylic acid [HA = benzoic (Hbz), salicylic (Hsal) or acetylsalicylic (Hacsal) acid] to give five-coordinate nickel(II) complexes of the type [Ni(mcN₃)(A)](PF₆). The complexes have been studied by spectroscopic methods (IR, UV-Vis and ¹H NMR). In acetone solution they exhibit isotropically shifted ¹H NMR resonances. The full assignment of these resonances has been made using one- and two-dimensional ¹H NMR techniques. The single-crystal structures of [Ni(Me₄-mcN₃)(bz)](PF₆), [Ni(Me₄-mcN₃)(sal)](PF₆) and[Ni(Me₄-mcN₃)(acsal)](PF₆) have been established by X-ray diffraction.