New linked macrocyclic systems. Interaction of palladium(ii) and platinum(ii) with tri-linked N2S2-donor macrocycles and their single-ring analogues

Abstract

Palladium(II) and platinum(II) complexes of ligands incorporating three linked, 16-membered, N₂S₂-donor macrocycles, together with their single-ring analogues have been synthesised. The former complexes are of the form [M₃L](PF₆)₆ (where M = Pd or Pt, and L is a linked three-ring macrocyclic species incorporating a 1,3,5-‘tribenzyl’ or a phloroglucinol core). The X-ray structure determination of the single ring species [PdL](PF₆)₂ (where L is a single N-benzylated derivative of the N₂S₂-donor macrocycle) showed that the palladium is coordinated to all four donor atoms of the macrocycle in a ‘square planar’ manner. The electrospray mass spectra of the tri-linked metal-containing species show a series of multiply charged ions resulting from the loss of hexafluorophosphate counter ions and hydrogens, and corresponding to [M −  nPF₆]ⁿ⁺ and [M −  nPF₆ −  mH]^{(n  −  m)+}. Expansion of individual charged peaks revealed the expected wide mass range resulting from the presence of three metal ions, each of which possesses a number of isotopes. Spectrophotometric titrations confirm that 3 ∶ 1 (metal ∶ ligand) stoichiometries occur for the complexes of these tri-linked ligands in acetonitrile.