Hydrogen Bonds Dictate the Coordination Geometry of Copper: Characterization of a Square‐Planar Copper(I) Complex

摘要

6,6′′‐Bis(2,4,6‐trimethylanilido)terpyridine (H2TpyNMes) was prepared as a rigid, tridentate pincer ligand containing pendent anilines as hydrogen bond donor groups in the secondary coordination sphere. The coordination geometry of (H2TpyNMes)copper(I)‐halide (Cl, Br and I) complexes is dictated by the strength of the NH–halide hydrogen bond. The CuICl and CuIICl complexes are nearly isostructural, the former presenting a highly unusual square‐planar geometry about CuI. The geometric constraints provided by secondary interactions are reminiscent of blue copper proteins where a constrained geometry, or entatic state, allows for extremely rapid CuI/CuII electron‐transfer self‐exchange rates. Cu(H2TpyNMes)Cl shows similar fast electron transfer (≈105 m−1 s−1) which is the same order of magnitude as biological systems.Entatischer Zustand: Wasserstoffbrücken diktieren die Geometrie von CuI‐ und CuII‐Komplexen. Eine ungewöhnliche quadratisch‐planare Geometrie am CuI‐Zentrum (siehe Struktur) wird als nahezu isostrukturell zum CuII‐Kern beobachtet. Die sehr geringe Reorganisationsenergie zwischen den Redoxzuständen ermöglicht einen extrem schnellen CuI/CuII‐Selbstaustausch.