Embracing ligands. A synthetic strategy towards new nitrogen–thioether multidentate ligands and characterization of the cobalt(iii) complexes

Abstract

The synthesis of the hexadentate ligand 2,2,9,9-tetra(methyleneamine)-4,7-dithiadecane (EtN 4 S 2 amp) is reported. The ligand is of a type in which bifurcations of the chain occur at atoms other than donor atoms. The cobalt() complex [Co(EtN 4 S 2 amp)] 3ϩ (1) was isolated and characterized. The synthetic methodology also results in a number of by-products, notably 2,9,9-tris(methyleneamine)-9-methylenehydroxy-4,7-dithiadecane (Et(HO)N 3 S 2 amp) and an eleven-membered pendant arm macrocyclic ligand 6,10-dimethyl-6,10-bis(methyleneamine)-1,4-dithia-8-azaacycloundec-7-ene (dmatue). The complexes [Co(Et(HO)3ϩ (2), in which the alcohol is coordinated to the metal ion, and [Co(dmatue)Cl] 2ϩ (4) were isolated and characterized. Et(HO)N 3 S 2 amp also undergoes complexation with cobalt() to produce two isomers endo- [Co(Et(HO)(exo-3), both with an uncoordinated alcohol group. endo-3 has the alcohol positioned cis, and exo-3 trans, to the sixth metal coordination site. Reaction of 1 with isobutyraldehyde, paraformaldehyde and base in dimethylformamide results in the encapsulated complex [Co(1,5,5,9,13,7,11,]-docosa-3,14-diene)](ClO 4 ) 3 ؒ2H 2 O ([Co(Me 6 docosadieneN 4 S 2 )] 3ϩ (5). All complexes have been characterized by single crystal X-ray study. The low-temperature (11 K) absorption spectrum of 1 has been measured in Nafion films with spin-allowed

Synthesis, characterization and DFT studies of the cobalt(iii) complex of a tetrapodal pentadentate N4S donor ligand

“…7 N 4 Samp arises from a deliberate synthetic strategy utilized previously to prepare a new set of hexadentate ligands known as amplectors. 7,8 Results and discussion…”

Embracing ligands. Synthesis, characterisation and the correlation between59Co NMR and ligand field parameters of Co(iii) complexes with a new class of nitrogen–thioether multidentate ligand

“…3 Replacing 1,2-ethanedithiol in that synthesis with 1,3-propanedithiol, 1,4-butanedithiol, and 1,2-xylenedithiol in the present synthetic procedures and subsequent complexation of the resulting ligands resulted in the isolation of [Co(RN 4 S 2 amp)] 3ϩ (R = Pr, Bu, Xy).…”

“…3 The chemical shifts of 13 C NMR spectra (D 2 O) for the metal complexes are reported in parts per million (δ C ) as positive downfield and negative upfield of the internal reference 1,4-dioxane, as described previously. Cyclic voltammetry and low resolution ESI mass spectrometry (ESI-MS) was performed as described previously.…”

“…1-3 These ligands, known as amplectors, 3 develop previously established themes in the coordination chemistry of thioether/nitrogen ligands. Our interest previously has been in the synthesis, electron transfer properties, and visible spectroscopy of complexes of nickel(), copper() and cobalt().…”

“…The series of complexes [Co(RN 4 S 2 amp)] 3ϩ reported in a previous paper (R = Et) 3 and in this work (R = Pr, Bu, Xy) (Chart 1), in combination with cobalt() complexes of homoleptic N 6 18-21 and heteroleptic (N 6Ϫx S x ; x = 1, 2, 3) ligands reported previously 3-8 offer an opportunity to explore further the relationship between 59 Co NMR shifts and the energies of the refers to the tetraamine-dithioether donor set of the ligand. Similar nomenclature applies to the BuN 4 S 2 amp and XyN 4 -S 2 amp systems.…”