The synthesis and characterization of a hetero‐dinuclear compound is presented, in which a copper(I) trishistidine type coordination unit is positioned directly above a zinc porphyrin unit. The close distance between the two coordination fragments is secured by a rigid xanthene backbone, and a unique (intramolecular) copper porphyrin‐π‐bond was determined for the first time in the molecular structure. This structural motif was further analyzed by temperature‐dependent NMR studies: In solution at room temperature the coordinative bond fluctuates, while it can be frozen at low temperatures. Preliminary reactivity studies revealed a reduced reactivity of the copper(I) moiety towards dioxygen. The results adumbrate why nature is avoiding metal porphyrin‐π‐bonds by fixing reactive metal centers in a predetermined distance to each other within multimetallic enzymatic reaction centers.

A bispyridylamine-based hanging unit within the ligand framework of a newly synthesized iron porphyrin complex (Py 2 XPFe) can act, on the one hand, as a hydrogen bonding site to facilitate proton transfer in catalysis and, on the other hand, as coordination site for a second Lewis acidic metal center. The bispyridylamine group in close proximity of the iron porphyrin center is able to mediate electrocatalytic CO 2 reduction in anhydrous MeCN. The hydrogen bonding interactions within the hanging group affect the kinetics of catalysis likely through stabilization of the [Fe I (CO 2 H)] À intermediate, increasing the overall rate of catalysis when compared to the non-functionalized analog, TMPFe (TMP = tetramesitylporphyrin). The rate constants (k app ) of the reduction reaction were calculated using the FOWA method which resulted in a higher TOF max for the complex Py 2 XPFe compared with TMPFe in neat MeCN (1.7 × 10 2 vs. 1.1 × 10 1 s À 1 ). The addition of weak Brønsted acids to the reaction mixture (TFE or PhOH) shows an increase in the rate of catalysis for both complexes, yet the Py 2 XPFe analog displays higher TOF max at each relative acid concentration, suggesting the hanging group beneficially impacts the rate of catalysis in the presence of these proton sources. The addition of Lewis acidic Sc 3 + to Py 2 XPFe also results in an increase in current density of the CO 2 reduction reaction. Resonance Raman as well as 1 H-NMR spectroscopy indicates coordination to the pyridine substituents.

New iron complexes [Cp*FeL]− (1‐σ and 1‐π, Cp*=C5Me5) containing the chelating phosphinine ligand 2‐(2′‐pyridyl)‐4,6‐diphenylphosphinine (L) have been prepared, and found to undergo facile reaction with CO2 under ambient conditions. The outcome of this reaction depends on the coordination mode of the versatile ligand L. Interaction of CO2 with the isomer 1‐π, in which L binds to Fe through the phosphinine moiety in an η5 fashion, leads to the formation of 3‐π, in which CO2 has undergone electrophilic addition to the phosphinine group. In contrast, interaction with 1‐σ—in which L acts as a σ‐chelating [P,N] ligand—leads to product 3‐σ in which one C=O bond has been completely broken. Such CO2 cleavage reactions are extremely rare for late 3d metals, and this represents the first such example mediated by a single Fe centre.

Neue Eisenkomplexe[ Cp*FeL] À (1-s und 1-p, Cp* = C 5 Me 5 )m it dem chelatisierenden Phosphininliganden 2-(2'-pyridyl)-4,6-diphenylphosphinin (L)w urden dargestellt und ihre Reaktion mit Kohlendioxid untersucht. Die Umsetzung mit CO 2 verläuft abhängig vom Koordinationsmodus von L in unterschiedlicher Weise.Mit dem Isomer 1-p,das eine h 4 -Koordination am Eisenatom aufweist, wird die elektrophile Addition an den Phosphininliganden unter Bildung des Komplexes 3-p beobachtet. Im Gegensatz hierzu reagiert das zweite Isomer 1-s,indem L als s-koordinierter [P,N]-Ligand vorliegt, zum C=O-Bindungsspaltungsprodukt 3-s.E ine solcheC O 2 -Spaltung wurdef ürs p äte 3d-Übergangsmetalle bisher sehr selten beobachtet, und wir berichten hier über das erste Beispiel mit einem einzelnen Eisenzentrum.

The Cover Feature shows an artist impression of the electrocatalytic reduction of CO2 by bispyridine‐bearing Fe porphyrin hangman complexes. In their Full Paper, A. R. Ramuglia et al. describe how this structural design achieves to permanently position metal cations in close vicinity to the Fe active site and thus allows for stabilisation of reaction intermediates, such as the high energy carboxylate intermediate, and hence accelerate the overall catalytic reaction. More information can be found in the Full Paper by A. R. Ramuglia et al.