Einfache Bildung eines beständigen Butadien‐2‐yl‐Kations: Stabilisierung durch Hyperkonjugation mit einer Al‐C‐Bindung

Abstract

Ein unerwartetes Produkt: Ein stabiles Butadien‐2‐yl‐Kation (rot im Bild) entsteht durch Hydroaluminierung von 1,4‐Di(tert‐butyl)butadiin mit Di(tert‐butyl)aluminiumhydrid. Seine Stabilisierung erfolgt insbesondere durch Hyperkonjugation mit einer Al‐C‐Bindung. Die Nucleophilie des kationischen Kohlenstoffatoms im Zwitterion reicht nicht aus, um das Hydridion aus der effektiven, chelatartigen Koordination durch beide Aluminiumatome zu lösen.

Differentiation rather than aging of muscle stem cells abolishes their telomerase activity

“…Durch zweifache Hydroaluminierung von Di(tert‐butyl)butadiin bildet sich die zwitterionische Verbindung (55), die ein kationisches Vinyl‐C‐Atom und ein durch die chelatisierenden Lewis‐sauren Al‐Zentren stabilisiertes Hydrid vereint 77)…”

A Phosphorus/Aluminum‐Based Frustrated Lewis Pair as an Ion Pair Receptor: Alkali Metal Hydride Adducts and Phase‐Transfer Catalysis

“…[11] To this end, we selected our recently reported, promising, and readily accessible geminal P/Al-based FLP 1 (Scheme 1), which does not require fluorinated substituents to enhance the Lewis acidity of the acceptor site. [14] The molecular structure of 2, obtained by a single-crystal X-ray structure determination ( Figure 1, top left), [15] shows a Li-H-Al three-center two-electron bond (Li1-H1 191 (2), Al1-H1 164(2) pm) with the Li atom connected to the phosphorus atom (Li1-P1 271.1(3) pm) [13,16] and two molecules of THF. A direct interaction of the lithium cation with the donor site of FLP 1 is indicated by the large 1 J(Li,P) coupling constant of 39.8 Hz [13] (d 7 Li = À0.3 ppm, 1 J(Li,H) = 14.8 Hz).…”

“…The hydride resides on the acceptor site, as can be deduced from the broad resonance at d 1 H = 2.91 ppm. [14] The molecular structure of 2, obtained by a single-crystal X-ray structure determination (Figure 1, top left), [15] shows a Li-H-Al three-center two-electron bond (Li1-H1 191 (2), Al1-H1 164(2) pm) with the Li atom connected to the phosphorus atom (Li1-P1 271.1(3) pm) [13,16] and two molecules of THF. This compound is the first structurally characterized monomeric lithium hydride complex.…”

Facile Synthesis of Aluminum‐Bridged [3,3,3]Cyclophanes by Hydroalumination

“…C-H bond activation by hyperconjugation with Al-C bonds and the chelating coordination of the resulting hydride anion by two aluminum atoms afforded 4 as a singular, persistent butadienyl cation (Scheme 1), which was zwitterionic and did not require the application of a strictly noncoordinating counterion for its stabilization. [9] In contrast, benzene centered tert-butylethynes showed a more complicated reaction behavior. Secondary reactions occurred that could be clarified completely for the more selective hydrogallation reactions only.…”