Sulphur-nitrogen chelating agents. VIII. Magnetic behaviour of some cobalt(II) complexes at the crossover region

Abstract

The bis-ligand cobalt(II) complexes of 6-methylpyrid-2-yi-N-(2?- methylthio-phenyl)methyleneimine (SNNMe) are spin-free and the corresponding complexes of 2-pyridyl-N-(2?- methylthiophenyl)methyleneimine (SNN) are spin-paired. This difference in magnetic behaviour arises from a lower effective ligand field strength of SNNMe, presumably due to the steric inter-ligand interference introduced by the methyl group in the 6-position of SNNMe. The moments of the cobalt(II) complexes are dependent on temperature and the departures from the Curie-Weiss law are quite anomalous. No quantitative treatment is given for the anomalous magnetic behaviour; however, the results are best explained as a thermal equilibrium between the nearly equi-energetic spin-paired and spin-free states of the cobalt(II) atom.

Ruthenium (II) complexes bearing thioether‐appended α‐iminopyridine ligands: Arene precursors permit access to κ2‐N,N and κ3‐N,N,S complexes

“…1 H NMR of 1 in DMSO‐ d 6 shows the expected number of signals, with clear separation between most resonances. A signal at δ = 8.95 attributed to the imine C–H is within the expected range for a coordinated aldimine . Four distinct doublets, each integrating for one proton were observed upfield of the aromatic region (δ = 6.06, 5.81, 5.73, and 5.33), suggesting that the p ‐cymene residue is bound to the Ru center in an η 6 fashion.…”

“…High purity reagents and solvents were purchased from Sigma‐Aldrich Ltd., Acros Organics, or Strem Chemicals Inc., and were used without further purification unless otherwise noted. Ligands L1 and L2 were prepared using reported literature procedures. Unless specifically noted, manipulations were conducted under inert atmosphere using standard air‐free techniques.…”

“…R = H) are known, these compounds are also known to isomerize to form the corresponding benzothiazoline or benzothiazole, or to generate the corresponding disulfide . Introduction of a thioether substituent blocks this tautomerization, enabling the preparation of complexes of pmtpm ( L1 , Scheme 1) featuring manganese(I), iron(II), cobalt(II), nickel(II/III), and ruthenium(II) centers . Early reports emphasized the structural homology between these complexes and the related metalloenzymes (e.g.…”

Ruthenium(II) Complexes Bearing Thioether-Appended α- Iminopyridine Ligands: Arene Precursors Permit Access to K2-N,N and K3-N,N,S Complexes

“…High purity reagents and solvents were purchased from Sigma-Aldrich Ltd., Acros Organics, or Strem Chemicals Inc., and were used without further purification unless otherwise noted. Ligands 1 56 and 2 58 were prepared using reported literature procedures. Unless specifically noted, manipulations were conducted under inert atmosphere using standard air-free techniques.…”

“…R = H) are known, these compounds are also known to isomerize to form the corresponding benzothiazoline or benzothiazole, or to generate the corresponding disulfide. [51][52][53][54][55] Introduction of a thioether substituent blocks this tautomerization, [56][57][58] enabling the preparation of complexes of pmtpm (1, Scheme 1) featuring manganese, 59 iron, 60 cobalt, 56 nickel, 61,62 and ruthenium. 63,64 Early reports emphasized the structural homology between these complexes and the related metalloenzymes (e.g.…”