Synthesis of Intramolecular P/Al‐Based Frustrated Lewis Pairs via Aluminum‐Tin‐Exchange and their Reactivity toward CO2. Issue 25 (22nd March 2022)

• Record Type: Journal Article
• Authors: Federmann, Patrick; Müller, Robert; Beckmann, Fabian; Lau, Caroline; Cula, Beatrice; Kaupp, Martin; Limberg, Christian
• Is Part Of: Chemistry. Volume 28:Issue 25(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-03-22
• Subjects: aluminum -- carbon dioxide -- FLP -- phosphane -- unimolecular; Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.202200404
• Languages: English
• ISSNs: 0947-6539

Abstract

Abstract: Frustrated Lewis pairs (FLPs) composed of acidic alane and basic phosphane functions, separated by a xanthene linker, can be prepared through the corresponding Me3 Sn derivative and methyl aluminum compounds with elimination of Me4 Sn. This way MeClAl‐, Cl2 Al‐ and (C6 F5 )2 Al‐ moieties could be introduced and the resulting FLPs are stabilized by a further equivalent of the alane precursors. In contact with the FLPs CO2 is bound via the C atom at the phosphane functions and the two O atoms at the Al centers. The residues at the latter determine the binding strength. Hence, in case of MeClAl CO2 capture occurs at higher pressure and under ambient conditions CO2 is released again, while for Cl2 Al and (C6 F5 )2 Al CO2 binding becomes irreversible. The results of DFT calculations rationalize these findings by the high thermodynamic stabilization in case of more electronegative residues, which concomitantly lead to higher barriers, and in case of (C6 F5 )2 Al further stabilization is achieved through a low reorganization energy. Abstract : Exchange of the players stannane and alane provides a viable route to intramolecular FLPs with large separations between Lewis acidic aluminum und Lewis basic phosphane functions. Neutral molecules occupy the space between the two moieties and are easily displaced by approaching substrates like CO2, which is spanned in the reaction pocket ‐ particularly strongly if the residues at the Al centers correspond to C6 F5 .