Synthetic, electrochemical, spectroscopic, and structural studies of mixed sandwich Co(III) complexes involving Cp or Cp* with tridentate N-donor and S-donor macrocycles

Abstract

The syntheses, structures, spectroscopy, and electrochemistry for four Co(III) mixed sandwich mononuclear complexes involving tridentate macrocycles and either cyclopentadienyl (Cp) or pentamethylcyclopentadienyl (Cp*) are reported. All complexes have the general formula [Co(CpR)([9]aneX3)](PF6)2, where X = S, 1,4,7-trithiacyclononane, and R = Cp (1) or Cp* (2), or X = N, 1,4,7-triazacyclononane, and R = Cp (3) or Cp* (4), and exhibit a pseudo-octahedral structure involving the carbocyclic η5-CpR ligand and facial κ3-donation from the macrocycle. The structures for all six complexes are supported by 1H and 13C{1H} NMR spectroscopy, and the compounds 1, 2, and 4 are also characterized by single-crystal X-ray crystallography. The 1H NMR shows an AA′BB′ splitting pattern for the coordinated macrocycle, and the dispersion between the two sets of multiplets is dependent upon the identity of the macrocycle. The [9]aneN3 complexes show only a single reversible (4) or irreversible (3) +3/+2 reduction in the −1.0 to −1.4 V range vs. Fc/Fc+. The [9]aneS3 complexes show the same reversible (1) or quasi-reversible (2) reduction in the −0.6 to −0.9 V range vs. Fc/Fc+ as well as a quasi-reversible (1) or irreversible (2) +2/+1 reduction in the −1.5 to −1.8 V range vs. Fc/Fc+.