Dimerisierung des Allylzink‐Kations: selektive Kupplung von Allylanionen in einer Metallo‐En‐Reaktion

The Bis(allyl)bismuth Cation: A Reagent for Direct Allyl Transfer by Lewis Acid Activation and Controlled Radical Polymerization

“…The allyl ligands in 3 coordinate to the metal center in an η 1 fashion. Thus, the coordination mode of allyl ligands in allyl bismuth compounds is retained upon cationization (σ vs. π bonding), as observed for allyl complexes of other Lewis acidic metals (La,13a Nd,13a Zn,13b Al,3c Ga3e). 14 Steric factors can be ruled out as a reason for the lack of π‐coordination, as bismuth cations with coordination numbers of up to eight have been reported 15.…”

Structurally Defined Allyl Compounds of Main Group Metals: Coordination and Reactivity

“…In solution, the allyl ligand shows fluxional behavior at ambient temperature, but an η 1 coordination mode can be frozen out at low temperatures 67. 68, 150 σ‐Type zinc–allyl interactions are also found for monocationic69 and monoanionic60, 150 allylzinc compounds in the solid state. In solution, the allyl‐exchange rate follows the order cationic<neutral<anionic.…”

“…71 At lower temperatures of 30 °C to 50 °C, bis(allyl)zinc undergoes an oligomerization in a metallo‐ene reaction 63b. This type of reaction was studied in detail for the allylzinc monocation69 (see Section 5.3.2). In general, bis(allyl)zinc is more reactive than di(alkyl)zinc reagents, as evidenced by the clean and rapid formation of vinylacetic acid from the reaction of bis(allyl)zinc with CO 2 followed by aqueous workup 63a…”

“…Recently, it was shown that this drawback can be overcome by using more Lewis acidic cationic allylzinc compounds instead of neutral species 69. These compounds dimerize in solvent‐dependent, reversible reactions (Scheme ), for which key thermodynamic and kinetic data were determined.…”

“… a) Dimerization of an allylzinc cation in a metallo‐ene reaction showing solvent‐dependent characteristics; [A]=[B(C 6 F 5 ) 4 ]; n =2 (isolated and dried compound), 3 (in situ reaction);69 b) alkali metal catalyzed dimerization of propene to give 4‐methylpent‐1‐ene 154…”