Transition metal chelates of some quinquedentate and tridentate ligands
Abstract
Transition metal chelates containing tridentate and
quinquedentate ligands have been prepared and studied.
Three bis-Schiff bases, N,N'-disalicylidene-4-R-2,
6-di(aminomethyl) anisole (R = Cl, Br, CH3) were
synthesized by the condensation of corresponding
diamines and salicylaldehyde. The bis-hydroxymethyl
derivatives of p-substituted phenolic ethers, were
treated with acetonitrile in presence of sulphuric
acid, to give the corresponding bis-amides, which on
hydrolysis gave the diamines. By the loss of two protons
the Schiff bases act as doubly nega tively charged M(ONONO)quinquedentate
ands,Storming neutral complexes of the
type M(ONONO) (M ='~i, Cu, Fe, Co). FAB mAss spectra
in all causes short the:parent protonated molecular ion
(M(NONOH) for each metal complex, except for copper,
where no such fan was observed . Although this could
indicate the presence of five-cordinate monomeric species
a detailed study of the electronic spectra suggests
otherwise. It is therefore concluded t ha t nickel (II),
copper(II), iron(II) and coba1t(II) form high-spin, po1ymeric
six-coordinate complexes, presumably with oxygen bridging.
However the uranyl complexes, U02(ONONO)
have a pentagonal bipyramidal structure with the
ligand acting as a dinegatively charged quinquedentate.
The Schiff base, N-salicylidene-6-aminomethyl-
.Z, 4-dichlorophenol was synthesized by the same
procedure as above. Due to the loss of two protons,
the Schiff base acts as doubly negatively charged
ONO-tridentate ligand and neutral copper complex of
the type CUZLZ was formed. A binuclear dimeric
structure has been suggested for the complex.
Structural elucidation entailed the use of
reflectance spectra, Fast Atomic Bombardment mass
spectra, X-ray diffraction patterns and magnetic
susceptibility. 1,he C, Hand N -micro analysis and
metal determination were carried out on all compounds
which were synthesized Gravimetric methods were used
to determine a~l metals (Ni, Cu, Co, Fe), except for
uranium which was determined by calorimetric method.