Synthesis and reactivity of five-coordinate nickel(II) and copper(II) complexes with a pentadentate ketoamine ligand

Abstract

A general method for the synthesis of hitherto unreported pentadentate fluorinated Schiff base ligands is presented. Two new five-coordinate metal complexes, Ni(tfacDPT) and Cu(tfacDPT), where H2(tfacDPT) is the pentadentate Schiff base derived from trifluoroacetylacetone and bis(3,3'-aminopropyl)amine, have been prepared and characterized by various physical techniques. Data for the Cu(II) complex indicate that it is square pyramidal while electronic spectra for the high spin Ni(II) complex suggest that it may possess a geometry intermediate between square pyramidal and trigonal bipyramidal. Ni(tfacDPT) coordinates with pyridine to produce a pseudooctahedral adduct, Ni(py)(tfacDPT), which releases pyridine in vacuo or on gentle heating of the complex.

The unexpected formation of biologically active Cu(II) Schiff mono-base complexes with 2-thiophene-carboxaldehyde and dipropylenetriamine: crystal and molecular structure of CudptaSCl2

“…Molar conductivities were measured on a WTW conductivity bridge employing a calibrated dip type cell and 10 À3 M MeOH and dimethyl sulfoxide (DMSO) solutions. Magnetic susceptibility (v M ) measurements on powder samples were performed at room temperature (25°C) employing the Gouy method on a home-built balance calibrated against Hg[Co(NCS) 4 ]. Diamagnetic corrections were estimated from PascalÕs constants.…”

“…Amongst these factors are either the protection of one of the two primary amino groups [1,2] or the partial hydrolysis of Schiff di-base metal complexes with the release of one aldehyde molecule. The hydrolytic reaction is promoted by using excess of Cu(II) salt and the separation of the mono base as insoluble product [3], or by acid catalysis [4]. The hydrolysis of the Schiff di-bases, for organic synthetic purposes, was achieved by use of 365 nm UV light [5].…”

Nickel(II) and copper(II) complexes of linear pentadentate ligands derived from substituted o-hydroxyaceto- and o-hydroxybenzophenones

“…A pentadentate ligand which is in a class by itself is that reported by Wallis and Cummings. 22 The ligand is formed by the Schiff base condensation of 2 mol of trifluoroacetylacetone with 1 mol of DPT. As a result of the rigidity of the acetylacetonimine segments of the ligand, the authors proposed an essentially square-pyramidal stereochemistry which differs somewhat from the structure which prevails among complexes of the more flexible ligands discussed above.…”

Cobalt(II) complexes of linear pentadentate Schiff base ligands

“…The synthesis of a new pentadentate ligand derived from trifluoroacetylacetone and DPT, If, has been recently reported; however complexation with cobalt(II) was not attempted. 4 Investigations involving ligands of this basic type in which the central donor atom is varied have not been published except for the report regarding cobalt(II) complexes of the ligand derived from salicylaldehyde and bis(2-aminoethyl) sulfide (DAES),5 Ie. Apparently the five-atom chain joining azomethine linkages is not long enough to allow coordination of the thioether sulfur because the complexes have properties characteristic of a tetrahedral geometry.…”