The mode of co-ordination of the quaternised 2,4′-bipyridinium cation. Crystal structures of trichloro(1′-methyl-2,4′-bipyridinium-χN1)platinum(II) dihydrate and dichloro(1′-methyl-2,4′-bipyridin-3′-ylium-χC3′, N1)platinum(II)

Abstract

The 1′-methyl-2,4′-bipyridinium ion (2,4′-mbipy⁺) reacts with K₂[MX₄](M = Pt^II or Pd^II; X = Cl or Br) to give the zwitterionic compounds [M(2,4′-mbipy)X₃]. The crystal and molecular structure of [Pt(2,4′-mbipy)Cl₃] has been determined by single-crystal X-ray analysis. The compound crystallizes in the monoclinic system, space group P2₁/c with a= 12.319(2), b= 9.359(1), c= 13.665(2)Å, and β= 107.90(1)°. From [M(2,4′-mbipy)X₃], cyclometallated [ML³X₂](M = Pt or Pd, X = Cl or Br, L³= 1′-methyl-2,4′-bipyridin-3′-ylium) has been synthesized and spectroscopically characterized. The crystal and molecular structure of [PtL³Cl₂] has been determined by single-crystal X-ray analysis. The compound crystallizes in the orthorhombic system, space group Pbca, a= 7.643(1), b= 17.726(2), and c= 17.142(2)Å. 2,4′-Bipyridyl (2,4′-bipy) reacts with PdX₂(X = Cl or O₂CMe) to yield trans-[Pd(2,4′-bipy)₂X₂] and with K₂[PtCl₄] to give cis-[Pt(2,4′-bipy)₂X₂]. Heating trans-[Pd(2,4′-bipy)₂X₂] in acetic acid gives the cyclometallated dimer [{PdL²(µ-O₂CMe)}₂](L²= 2,4′-bipyridin-3-ylium).