Synthesis and Structural Characterisation of Copper(II) 15‐Metallacrown‐5 Complexes with Pb^II, Hg^II, Ag^I, Na^I and Y^III Central Metal Ions

Abstract

Abstract The new copper(II) 15‐metallacrown‐5 complexes with the central metal ions Pb II , Hg II , Ag I , Na I and Y III , with the formula [MCu 5 L 5 ]X n {H 2 L is 2‐picolinehydroxamic acid or ( S )‐phenylalaninehydroxamic acid and X – is NO 3 – or Cl – }, have been synthesised and characterised by NMR and UV/Vis spectroscopy, electrospray mass spectrometry and elemental analysis. The Pb II ‐ and Hg II 15‐metallacrown‐5 complexes were obtained in the crystalline form as pyridine adducts [PbCu 5 (picha) 5 (py) 6 ](NO 3 ) 2 · 3(py) and [HgCu 5 (picha) 5 (py) 7 ](NO 3 ) 2 · 2(py) and their X‐ray crystal structures were determined. In both complexes, each peripheral Cu II ion of the metallacrown is coordinated by one pyridine molecule bonded in the axial position. In the case of the Pb II derivative, one additional axial pyridine molecule is bound to the central metal ion, while in the case of the Hg II derivative, two axial pyridine ligands are bound to the central Hg II ion. The relative stability of the copper(II) 15‐metallacrown‐5 complexes with various central metal ions was determined on the basis of competition reactions. The relative preference of the 15‐metallacrown‐5 system for the central metal ion follows the series Na I , Ag I < lanthanide(III), Hg II < Pb II .(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)