NO Donor Ligand Research Articles

Synthesis and structure of a ‘4 + 1’ oxorhenium(V) complex containing imidazole derivatives

The ‘4 + 1’ concept was used to prepare the complex salt [ReO(iao)Br]Br (1) from the reaction of (n-Bu4N)[ReOBr4(OPPh3)] with the ligand bis{2′-methyl(1′-methylimidazole)}-2-aminoethanol (Hiao) in methanol. The single-crystal X-ray crystal structure of 1 shows that iao acts as a monoanionic, tetradentate, N3O-donor chelate. When the reaction was carried out in acetonitrile, the neutral complex [ReO(iao)Br2] (2) was isolated. Elemental analyses and IR data suggest that iao acts as a tridentate, N2O-donor ligand in 2.

Oxovanadium(IV, v) complexes of salicylidene-2-picoloyl hydrazone Schiff base and related ligands

Oxovanadium(iv,v) complexes having O 4 N coordination environment have been synthesized in the solid state, formulated as M[VO 2 (L/L',/L)(H 2 O)], where M = K or NH 4 ; H 2 (L/L'/L) is the Schiff base ligand, obtained by condensation of salicylaldehyde with 2-picoloyl (L), 2-quinoloyl (L'), 8-quinoloyl (L) hydrazides. Dimeric complexes having the formulation [(VOL) 2 μ-O] have also been synthesized. Both the salicylidene-picoloyl hydrazone and the salicylidene-2-quinoloyl hydrazone ligands, in their dideprotonated form, coordinate to both vanadium in its +4 and +5 slate, through 0, N, O donor atoms, while, the ligand H 2 will act as a NNO donor ligand. Thus, in the dioxo vanadium complexes with the ligands L and L', the central vanadium core will have the O 4 N environment, which can be treated as a model to mimic the active site of vanadium haloperoxidases.

Synthesis of a Four-Strand N2O2-Donor Ligand and its Transition Metal Complexation Probed by Electrospray Ionisation Mass Spectrometry

The four-strand and potentially N2O2-donor ligand 2,3-endo,endo-bis(aminomethyl)-5,6-endo,endo-bis(hydroxymethyl)bicyclo[2.2.1]heptane (L1), a close analogue of the known tetraalcohol 2,3,5,6-endo,endo,endo,endo-tetrakis(hydroxymethyl)bicyclo[2.2.1]heptane (L2), has been prepared via a multi-step synthesis and isolated as the copper(II) complex [Cu(L1)2](ClO4)2. An ESI-MS study of the complex and metal ion exchange with other transition metal ions (Fe2+, Co2+, Ni2+, Mn2+ or Zn2+) indicates that 1:1 complexes form readily. Apparently special stability for the Ni2+ species observed in the ESI-MS study suggests strong encapsulation of this ion.

Studies on galactose oxidase active site model complexes: effects of ring substituents on Cu(II)-phenoxyl radical formation

Copper(II) complexes of new N 3O- and N 2O 2-donor tripodal ligands bearing one or two o-substituted phenol moieties have been synthesized as models for the galactose oxidase active site. The complexes of 2-[ N-(1-methyl-2′-imidazolylmethyl)- N-(6″-methyl-2″-pyridylmethyl)-aminomethyl)]-4-methyl-6-methylthiophenol (MeSL), [Cu(MeSL)Cl], and N-(6-methyl-2-pyridylmethyl)- N, N-bis(2′-hydroxy-3′,5′-di- tert-butylbenzyl)amine (t-buL2mepy), [Cu(t-buL2mepy)(H 2O)], have been revealed by X-ray structural analysis to have a square-pyramidal structure with one and two phenolate oxygens in the basal plane, respectively. [Cu(MeSL)Cl] was converted into a Cu(II)- o-methylthiophenoxyl radical species by electrochemical or Ce(IV) oxidation. An o-methoxyphenoxyl radical in a similar complex was considerably more stable than the 2,4-di( tert-butyl)phenoxyl radical. While t-buL2mepy reacted with Cu(ClO 4) 2 to give [Cu(t-buL2mepy)(H 2O)] without disproportionation, an N2O2-donor ligand containing an o-methoxyphenol, a 2,4-di( tert-butyl)phenol, and an N-methylimidazole moiety gave a phenoxyl radical complex exhibiting the characteristic absorption peak at 478 nm as a reddish powder by the reaction with Cu(ClO 4) 2 as a result of spontaneous disproportionation. It exhibited a quasi-reversible redox wave at E 1/2=0.34 V (vs. Ag/AgCl) in CH 3CN, which is lower than the potentials of the copper complexes of various N 3O-donor ligands, and oxidized ethanol to acetaldehyde with a low turnover number.

Studies of V(III) complexes with selected α-N-heterocyclic carboxylato NO donor ligands: structure of a new seven-coordinated pentagonal bipyramidal complex containing picolinato ligands

Some highly stable V(III) complexes involving the biologically important and chemically interesting ONO donor ligand pyridine-2,6-dicarboxylic acid (dipicolinic acid, DPAH2) are reported. They include both homo- and hetero-chelates involving DPAH2 and some other bidentate chelating ligands and one of them is a new highly stable seven- coordinated mononuclear V(III) complex, [V(DPA)(PA)(H2O)2]·H2O 4 (PA = picolinate anion). The complex 4 containing two different α-N-heterocyclic carboxylates has a pentagonal bipyramidal structure with the equatorial plane accommodating the ONO and NO donor points while the two water molecules occupy the axial positions.

Elaboration of the bis(pyrazolyl)hydroborato ligand [Bp Bu t,Pr i] into the NNO donor ligand, [(MeO)Bp Bu t,Pr i]: Structural characterization of a complex in which the [(MeO)Bp Bu t,Pr i] ligand models the binding of zinc to the peptide backbone in thermolysin

The bis(pyrazolyl)hydroborato ligand in (Bp Bu t ,Pr i)ZnMe is converted to the NNO donor ligand in [ η 3-(MeO)Bp Bu t , Pr i ]ZnMe by insertion of [CH 2O] into one of the BH bonds; structural characterization by X-ray diffraction confirms that the ligand binds to the zinc centre a in manner analogous to the binding of zinc to the peptide backbone in thermolysin.

Synthesis of 4′,5′-Bis(salicylideneimino)benzo[15-crown-5] and Its Complexes with Uranyl(VI), Copper(II), Nickel(II), and Cobalt(II)

Abstract 4′,5′-Bis(salicylideneimino)benzo{15-crown-5} (SALH2) has been synthesized from 4′,5′-diaminobenzo{15-crown-5} and salicylaldehyde. The crystalline sodium nitrate complex of the ligand (SALH2.NaNO3.H2O) has also been isolated. As an N2O2-donor ligand, SALH2 forms 1:1 metal complexes with various metals {SAL(M)xH2O where M = UO2(VI), Cu(II), or Ni(II)}. The octahedral Co(II) complex of SALH2 is capable of binding molecular oxygen. Also prepared were the complexes which simultaneously contain both sodium and transition metal ion. 1H-n.m.r., i.r., u.v.-visible, and conductance data are presented.

New mixed ligand complexes of Co(III) containing ethylenediamine, propylenediamine and some bidentate NN, OO and NO donor ligands

New mixed ligand complexes of Co(III) containing ethylenediamine, propylenediamine and some bidentate NN, OO and NO donor ligands

STUDIES ON MIXED LIGAND COMPLEXES, PART II. COBALT(III) HETEROCHELATES CONTAINING NONPLANAR QUADRIDENTATE LIGANDS

Abstract A series of new cobalt (III) mixed ligand complexes of the type [Co(AA) (BBBB)] [where AA = bidentate monobasic NO or OO donor ligands such as picolinic acid, quinaldinic acid, acetylacetone, tropolone, acetoacetanilide, N-benzoylphenyl-hydroxylamine, benzohydroxamic acid, and BBBB = quadridentate ONNO donor ligand like N,N′-trimethylenediaminebis (salicylideneimne)(saltnH2)] were synthesized and characterized by elemental analysis, conductance measurements, electronic spectra, infrared spectra, molecular weight and magnetic susceptibility measurements. The complexes are green in color, monomers, non-electrolytes and diamagnetic. In these heterochelates the quadridentate ligand saltn adopts an unusual nonplanar twisted conformation and the bidentate ligand occupies two cis positions. The magnetic and electronic spectral data of the complexes indicate distorted octahedral structure of the complexes. Electronic spectral data in non-coordinating and coordinating solvents indicate that the heterochel...