Crystal and molecular structure of [N, N′-ethylenebis(methyl-2-amino-1-cyclopentenedithiocarboxylato)]copper(II): A quantitative relationship between tetrahedral distortion and redox potentials in copper N2S2 compounds and the relevance to type I copper(II) centers

An Unusual Cu(II) Mediated C–N Single Bond Cleavage of Pentacoordinating N4S Ligands: Control of Copper Coordination Geometry by Modified Ligand Structure

“…Again in the series 2a-4a, the Cu(II)/Cu(I) reduction becomes more difficult (E½ more negative) in going from 2a to 4a when the geometry around copper becomes more towards tetrahedral. This is contrary to the expectation mentioned earlier that copper(II) in tetrahedral geometry favours the Cu(II)/Cu(I) reduction [38,39]. This unusual trend is due to the weak coordination of alkoxy group to the Cu(II) center in solution which makes the metal center electronically richer in going from 2a to 4a with the increase in donor strength of alkoxy group.…”

“…Compound 5 with almost a planar geometry (dihedral angle 8.8º(5)) is more difficult to reduce (E½ = − 0.34 V) than its counterparts 2a-4a and 2b-4b (E½ range − 0.18 to − 0.22 V) with geometries distorted more towards tetrahedral. This is however, not unexpected, considering the preference of copper(I) for tetrahedral geometry [38,39]. Again in the series 2a-4a, the Cu(II)/Cu(I) reduction becomes more difficult (E½ more negative) in going from 2a to 4a when the geometry around copper becomes more towards tetrahedral.…”