Substituierte Alkinyle als axiale Liganden an häminähnlich gebundenem Eisen(III) ‐ Einordnung in eine spektrochemische Serie

Abstract

Substituted Alkinyles as Axial Ligands at Hemine Like Bound Iron(III) ‐ Incorporation into a Spectrochemical Series.Substituted lithium alkynyles LiCCR (R = tBu, Ph, p‐ClC6H4, Me3Si, iPr3Si, Ph3Si) react with the hemine like macrocyclic iron(III) complex 6,13‐di(ethoxycarbonyl)‐5, 14‐dimethyl‐1, 4, 8, 11‐tetraazatetradeca‐4,6,12,14‐tetraenato[2−]iron(III)‐iodide (formula 2;) in tetrahydrofuran to form anionic low‐spin di‐adducts [fe(CCR)2]−. The incorporation of the alkynyles into a spectrochemical series of the axial ligands (studied by the sharp equatorial‐ligand‐to‐metal CT absorption band) results in the wavelength‐sequence (nm): OH− (≈︁ 510) « N3− (≈︁ 625) < tBuCC− (664) < NH3 (666) < PhCC− (692) < PhNH2 (695) < Me3SiCC− (698) < SCN− (713) < Ph3SiC  C− (716) < CN− (739) < 4‐picoline (759) < pyridine (765) < nicotinamide (776) < methylnicotinat (788) < pyrazine (798) and points to a significant π‐acceptor ability of the silyl substituents.