Novel base-free dianion complexes of Pt(II) and Pd(II) derived from heterocyclic thiourea and tertiary phosphine ligands

Abstract

Treatment of one molar equivalent of [M(HCPPT)2] (M=Pd, Pt; H2CPPT = 1-(5-chloropyridin-2-yl)-3-phenylthiourea) with one molar equivalent of κ2-diphos (diphos = dppe, dppp, dppb, and dppf) or two molar equivalent of κ1-phos afforded eight heterocyclic thiourea dianion complexes (1–8). The spectroscopic data analysis showed clear AX splitting pattern, which indicates that the two coordinated phosphorus atoms are non-equivalent. Meaning that, the metal's center is attached to both S,N donor atoms in a chelating fashion. In addition, the splitting system show a good resemblance to the previously synthesized thiourea dianion complexes. Furthermore, the reaction is believed to undergo a square planar substitution mechanism at which five coordinate intermediate is formed. Generally, the reported complexes (1–8) are believed to resemble their analogues thiourea dianion complexes at which a four membered ring structure is formed with Pt(II) or Pd(II) being centered, adopting a square planar geometry. Four of the synthesized complexes (1–4) were tested against Salmonella typhimurium and Bacillus subtilis bacteria at which complexes 4 and 2 showed highest activity values.