The Chemistry of a Non‐Interacting Vicinal Frustrated Phosphane/Borane Lewis Pair

Abstract

The dimesitylphosphinocyclopentene/HB(C F ) -derived vicinal trans-1,2-P/B frustrated Lewis pair (FLP) 4 shows no direct phosphane-borane interaction. Toward some reagents it behaves similar to an intermolecular FLP; it cleaves dihydrogen, deprotonates terminal alkynes, and adds to organic carbonyl compounds including CO . It shows typical intramolecular FLP reaction modes (cooperative 1,1-additions) to mesityl azide, to carbon monoxide, and to NO. The latter reaction yields a persistent P/B FLPNO nitroxide radical, which undergoes H-atom abstraction reactions. The FLP 4 serves as a template for the CO reduction by [HB(C F ) ] to generate a FLP-η -formylborane. The formylborane moiety is removed from the FLP template by reaction with pyridine to yield a genuine pyridine stabilized formylborane that undergoes characteristic borane carbaldehyde reactions (Wittig olefination, imine formation). Most new products were characterized by X-ray diffraction.

Reversible C−H Activation, Facile C−B/B−H Metathesis and Apparent Hydroboration Catalysis by a Dimethylxanthene‐Based Frustrated Lewis Pair

“…These NMR shifts are in good agreement with data previously publishedf or zwitterionic phosphonium/alkynylborate compounds formed via the reactions of FLPs with phenylacetylene. [14] The 31 Pa nd 1 HNMR spectra of 2a in CD 2 Cl 2 ,h owever,a lso feature signals due to the FLP 1a and free phenylacetylene, which we hypothesized might be due to the presence of an equilibrium between PhCCH and its CÀHa ctivated form at room temperature. [14] The 31 Pa nd 1 HNMR spectra of 2a in CD 2 Cl 2 ,h owever,a lso feature signals due to the FLP 1a and free phenylacetylene, which we hypothesized might be due to the presence of an equilibrium between PhCCH and its CÀHa ctivated form at room temperature.…”

“…For example, Erker et al report 11 Ba nd 31 PNMR shifts of d B = À17.6 and d P = 1.6 ppm ( 1 J PÀH = 490 Hz) for the product of CÀHc leavage by an anthracene-based intramolecular FLP, [13] and d B = À16.5 and d P = 0.0 ppm ( 1 J PÀH = 470 Hz) for ac yclopentanederived system. [14] The 31 Pa nd 1 HNMR spectra of 2a in CD 2 Cl 2 ,h owever,a lso feature signals due to the FLP 1a and free phenylacetylene, which we hypothesized might be due to the presence of an equilibrium between PhCCH and its CÀHa ctivated form at room temperature. Investigationb yv ariable temperature NMR spectroscopy revealed that the relative proportionso f1a/2a vary as af unction of temperature (K = 5.4 mm at 308 Kf or the loss of PhCCH;0 .61 mm at 198 K), and aV an't Hoff analysis (see Supporting Information) yields thermodynamic data (DH q =+34 kJ mol À1 ; DS q =+68 Jmol À1 K À1 )f or the loss of PhCCH from 2a.T hese data can be put into context by the corresponding values of + 38 kJ mol À1 and + 102 Jm ol À1 K À1 for the loss of H 2 from the phosphonium borate derived from the related FLP 1b.…”

Aromaticity‐promoted CO2 Capture by P/N‐Based Frustrated Lewis Pairs: A Theoretical Study

“…In series II , FLPs in the close form are thermodynamically more stable, leading to relatively higher activation barriers (17.3–29.6 kcal mol −1 ) because breaking P…N bonding interaction is required for CO 2 activation. Similarly, Erker et al . reported that the development of open, non‐interacting and intramolecular P/B FLPs is significant towards small molecule activations including CO 2 .…”

Erster Ryoji‐Noyori‐ACES‐Preis: C.‐M. Che / Ehrenmitglied der japanischen chemischen Gesellschaft: G. Erker

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Die japanische chemische Gesellschaft (CSJ) ehrte kürzlich bei ihrem Jahrestreffen eine Reihe herausragender Wissenschaftler, darunter Graham Fleming (University of California, Berkeley) und Gerhard Erker (Universität Münster) mit Ehrenmitgliedschaften für ausländische Forscher. Von Erker erschien in der Angewandten Chemie eine Arbeit über die metallfreie Allen‐Cyclotrimerisierung und in Chemistry—A European Journal eine über ein nicht wechselwirkendes benachbartes frustriertes Phosphan‐Bor‐Lewis‐Paar . Erker studierte an der Universität zu Köln und der Ruhr‐Universität Bochum.…”