Dipyrromethene complexes of transition metals. Part III. Physical properties and crystal and molecular structure of a mixed-ligand complex of palladium(II)

Abstract

Complexes have been formed between bivalent palladium and the dipyrromethene ligands 4,4′-bis(ethoxycarbonyl)-3,3′,5,5′-tetramethyldipyrromethene (mpmH) and 3,4′-bis(ethoxycarbonyl)-5-chloro-3′,4,5′-trimethyldipyrromethene (cpmH) of the type Pd₂Cl₂L₂(L = mpm or cpm) and PdXL(LH)(X = Cl or Br; L = mpm or cpm; LH = mpmH or cpmH). The latter complexes contain both bi- and uni-dentate co-ordinated dipyrromethene ligands. The ¹H n.m.r. and u.v.–visible spectra of these complexes have been investigated and an X-ray determination (diffractometer data) of the crystal and molecular structure of PdCl(cpm)(cpmH) is reported. The palladium atom is in an essentially square planar environment bonded to three nitrogen atoms and one chlorine atom. The uni- and bi-dentate dipyrromethene ligands deviate considerably from planar configurations. The unco-ordinated nitrogen atom lies above the palladium square plane but does not seem chemically bonded to any atom in the plane. Crystals are monoclinic, space group Cc, Z= 4, a= 1782(1), b= 2096(1), c= 1038(6) pm, β= 95·47(3)°. The structure was solved by Patterson and Fourier methods and refined by least-squares techniques to R 5·7%(2257 independent reflections).