Facile C=O Bond Splitting of Carbon Dioxide Induced by Metal–Ligand Cooperativity in a Phosphinine Iron(0) Complex

Abstract

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.

Cooperative CO2 Scission by Anomalous Insertion into a Rh–Si Bond

“…We expect that the more electronegative late metals (Ru, Os, Rh, Ir, Pd, Pt) may all exhibit a similar anomalous insertion process with CO 2 , including at other metal/main-group σ bonds (e.g., boryl, germyl, and phosphide complexes). This notion is supported by the recent report of CO 2 splitting in a similar fashion to that reported here at the Fe–P bond of an iron(0) phosphinine complex . In general, this work has demonstrated how the electronic façade of a metal/main-group unit impacts the selectivity of insertion reactions.…”

Synthesis and Characterization of Bidentate Isonitrile Iron Complexes

“…Some of us have previously been interested in the synthesis and reactivity of low-oxidation-state polyarene and alkene ferrates . Such complexes have been used for various applications, including the activation of small molecules (e.g., P 4 and CO 2 ) and as catalysts for hydrogenation and hydroboration reactions . Taking advantage of the well-known ability of isonitriles to stabilize low-oxidation-state transition-metal complexes, − , in combination with imposing rigidity, we were interested in exploring the potential of the aforementioned chelating isonitrile ligands in the stabilization of highly reduced iron complexes.…”

C=O‐Bindungsspaltung in Kohlendioxid durch einen Eisen(0)‐Phosphininkomplex

“…Abbildung 3. Molekülstruktur von 2 im Festkçrper; [24] Intuitiv lässt sich die Bildung von 3-s und 3-p jeweils aus der direkten Reaktion von CO 2 mit 1-s und 1-p erklären. Diese Vermutung wird durch die 31 P{ 1 H}-NMR-Spektren der Reaktionsmischung bestätigt, die 3-s und 3-p in demselben Integralverhältnis von 2:1zeigen, wie es auch für 1-s and 1-p beobachtet wird (siehe oben).…”

“…Molekülstruktur von 1-s im Festkçrper (links);[24] Ellipsoide sind mit 40 %Aufenthaltswahrscheinlichkeit gezeichnet; füreine bessere Anschaulichkeit sind H-Atome nicht gezeigt, und das [K-([18]Krone-6)] + -Kation ist transparent; ausgewählte Bindungslängen [] und Bindungswinkel [8 8]: Fe1-P1:2.0811(4), Fe1-N1:1 .9428(12), P1-C1: 1.7733(13), C1-C2:1 .3953(19), C2-C3:1.3947(18),C 3-C4:1 .4343(18), C4-C5:1 .3756(18), C5-P1:1.7757(13),P 1-Fe1-N1:8 2.32(4), Fe1-P1-C1: 107.62(4), Fe1-N1-C6:124.18(9), Cp*-Fe1-N1:135.513(8),P 1-Fe1-Cp*: 140.545(9). Seitenansicht der Molekülstruktur von 1-s im Festkçrper (rechts);zur Anschaulichkeit ist eine weitere Phenylgruppe transparent dargestellt.…”