Reversible Carbon Dioxide Binding by Simple Lewis Base Adducts with Electron-Rich Phosphines

Abstract

For the efficient utilization of carbon dioxide as feedstock in chemical synthesis, low-energy-barrier CO2 activation is a valuable tool. We report a metal-free approach to reversible CO2 binding under mild conditions based on simple Lewis base adducts with electron-rich phosphines. Variable-temperature NMR studies and DFT calculations reveal almost thermoneutral CO2 binding with low-energy barriers or stable CO2 adduct formation depending on the phosphines donor ability. The most basic phosphine forms an air-stable CO2 adduct that was used as phosphine transfer agent, providing a convenient access to transition-metal complexes with highly electron-rich phosphine ligands relevant to catalysis.

Switching the Electron‐Donating Ability of Phosphines through Proton‐Responsive Imidazolin‐2‐ylidenamino Substituents

“…For our study, we selected the IAPs P(R 1 )( i Pr) 2 ( 1 ) and P(R 1 ) 2 ( i Pr) ( 2 ), which carry one and two 1,3‐diisopropyl‐4,5‐dimethylimidazolin‐2‐ylidenamino groups (R 1 ), respectively. Phosphines 1 and 2 can be conveniently prepared by deprotonation of imine R 1 H with n ‐butyllithium followed by treatment with the respective chlorophosphines . However, the separation of lithium chloride from the IAPs can be challenging due to complexation by the imino N atoms .…”

“…To explore the proton‐responsive properties of IAPs we prepared complexes 3 and 4 through the reported procedures as well as the palladium complex 5 from the reaction of phosphines 1 with [PdCl 2 (MeCN) 2 ] (Schemes ). Treatment of complex 3 with 2,6‐lutidinium triflate gave complex 3 ⋅HOTf as a white solid in quantitative yield.…”

Accessing Frustrated Lewis Pair Chemistry from a Spectroscopically Stable and Classical Lewis Acid‐Base Adduct

“…Whereas classical FLPs such as t Bu 3 P/B(C 6 F 5 ) 3 ,r equire the simultaneous action of the Lewis acid and base on CO 2 to effect capture of this small molecule,the present system appears to react in as tepwise manner (Figure ). [14,17] While the formation of 1-CO 2 is not observable by NMR spectroscopy,i ta ppears this species is trapped by B(C 6 F 5 ) 3 . [14,17] While the formation of 1-CO 2 is not observable by NMR spectroscopy,i ta ppears this species is trapped by B(C 6 F 5 ) 3 .…”

Phosphazenylphosphine: Die elektronenreichsten ungeladenen Brønsted‐ und Lewis‐Phosphor‐Basen

“…[13] 2017 wurde das Problem der Guanidinzersetzung von Dielmann et al gelçst, indem ein Imidazol-2-ylidenamin als Guanidin-/ Imidazol-artiger Substituent gewählt und so die Klasse elektronenreicher Phosphane (IAPs) mit hoher Basizitätu nd niedrigen elektronischen Tolman-Parametern (TEPs) zugänglich gemacht wurde. [14,17] In der Tatstellen die über eine einfache Synteseroute darstellbaren PA Ps die stärksten ungeladenen PR 3 -Donoren dar und übertreffen sogar IAPs bezüglich ihrer hçheren pK BH þ -u nd niedrigeren TEP-Werte.I nA nlehnung an Schwesingers Phosphazene führen wir folgende Nomenklatur ein:" (R 2 N)P V x P III "b ezeichnet eine P III -Base,b estehend aus x Phosphazenyleinheiten. Die daraus resultierende Klasse der Phosphazenylphosphine (PAPs) ist, anders als Phosphazene,z usätzlich privilegiert, eine große Anzahl an Übergangsmetallkomplexen zu bilden.…”