Carbonylation Reactions of Intramolecular Vicinal Frustrated Phosphane/Borane Lewis Pairs

Abstract

The intramolecular frustrated Lewis pair (FLP) Mes2PCH2CH2B(C6F5)2 4 adds cooperatively to carbon monoxide to form the five-membered heterocyclic carbonyl compound 5. The intramolecular FLP 7 contains an exo-3-B(C6F5)2 Lewis acid and an endo-2-PMes2 Lewis base functionality coordinated at the norbornane framework. This noninteracting FLP adds carbon monoxide in solution at -35 °C cooperatively to yield a five-membered heterocyclic FLP-carbonyl compound 8. In contrast, FLP 7 is carbonylated in a CO-doped argon matrix at 25 K to selectively form a borane carbonyl 9 without involvement of the adjacent phosphanyl moiety. The free FLP 7 was generated in the gas phase from its FLPH2 product 10. A DFT study has shown that the phosphonium hydrido borate zwitterion 10 is formed exergonically in solution but tends to lose H2 when brought into the gas phase.

Frustrated Lewis Pair Chemistry: Development and Perspectives

“…Interestingly 125 is thermally robust (80 8C for over 24 h). [103] The analogous reactions of FLPs with SO 2 afford the inter-and intramolecular FLP adducts t Bu 3 PSO 2 B(C 6 F 5 ) 3 (126) and Mes 2 P(CH 2 ) 2 B(C 6 F 5 ) 2 (SO 2 ) (127). [105] While the connectivity is similar to that of the CO 2 adducts, these species exhibit a pseudo-pyramidal geometry and thus a center of chirality at the S atom.…”

“…[125] Some saturated vicinal P/B and N/B FLPs exhibit similar behavior toward carbon monoxide. For example, both the FLPs 93, 8 [126] and boron-imidinates HC(NR) 2 B(C 6 F 5 ) 2 [87] (R = i Pr, t Bu) reacted with CO by cooperative P/B addition to form the bridged carbonyl adducts 178-181, respectively (Scheme 60). These compounds were characterized by X-ray diffraction and spectroscopy (178-181: IR: ñ(CO) = 1791, 1714, 1713 cm À1 ).…”

Stabile Heterocyclopentan‐1,3‐diyle

“…[18][19][20] Jüngste Berichte über Carbonylierungen mit frustrierten Lewis-Paaren regten unser Interesse an der Aktivierung von CO durch Singulett-Biradikaloide an. [21,22] Für CO kann weder der 1,1-noch der 1,2-verbrückende Bindungsmodus günstig sein, da für den Erstgenannten eine hohe Ringspannung innerhalb des [1.1.1]Bicyclus auftritt, während der Zweitgenannte ein ungewçhnli-ches Carben wäre. Wir berichten hier über die Carbonylierung des Diphosphadiazandiyls, die die Synthese des ersten stabilen Cyclopentan-1,3-diyls durch eine ungewçhnliche Ringerweiterung ermçglichte.…”

CO/CO and NO/NO coupling at a hidden frustrated Lewis pair template

“…Compound 1 adds both the phosphane Lewis base and the borane Lewis acid to the CO carbon atom to yield the five-membered heterocyclic carbonyl compound 2 . 4 This behavior of FLP 1 remotely resembles CO/metal coordination chemistry 5 and in contrast to the conventional role of such P/B pairs as ambiphilic ligands. 6 Compound 1 reacts analogously with nitric oxide (NO), again serving in a “pseudo-metal like” role, giving the persistent nitroxide radical 3 (see Scheme 1).…”