Synthesis, characterisation and speciation studies of heterobimetallic pyridinehydroxamate-bridged Pt(ii)/M(ii) complexes (M = Cu, Ni, Zn). Crystal structure of a novel heterobimetallic 3-pyridinehydroxamate-bridged Pt(ii)/Cu(ii) wave-like coordination polymer

Abstract

The reaction of cis-[Pt(NH₃)₂(3-pyhaH)₂]²⁺ (3-pyhaH = 3-pyridinehydroxamic acid) and cis-[Pt(NH₃)₂(4-pyhaH)₂]²⁺ (4-pyhaH = 4-pyridinehydroxamic acid) with Cu(II), Ni(II) or Zn(II) in aqueous solution affords novel heterobimetallic pyridinehydroxamate-bridged complexes, {cis-[Pt(NH₃)₂(µ-3-pyha)M(µ-3-pyha)]·SO₄·xH₂O}_n and {cis-[Pt(NH₃)₂(µ-4-pyha)M(µ-4-pyha)]·SO₄·xH₂O}_n respectively. The crystal and molecular structure of one of these, {cis-[Pt(NH₃)₂(µ-3-pyha)Cu(µ-3-pyha)]SO₄·8H₂O}_n3a, has been determined and was found to be a novel heterobimetallic wave-like coordination polymer, the structure of which contains interlinked pyridinehydroxamate-bridged repeating units of Pt(II) and Cu(II) ions in slightly distorted square-planar N₄ and O₄ coordination environments respectively and extensive hydrogen-bonding through the Pt ammines and the deprotonated hydroxamate O and via the O of the SO₄²⁻ counterions and the H(N) of the hydroxamate moiety. Spectrophotometric and speciation studies on the other heterobimetallic systems confirm that very similar species are being formed in solution and based on elemental analysis and spectroscopic results analogous complexes are formed in the solid-state. In this paper, we report the first examples of coordination polymers incorporating both Pt(II)/Cu(II), Pt(II)/Ni(II) and Pt(II)/Zn(II) and containing pyridinehydroxamic acids as bridging scaffolds.