Synthesis of an Extremely Bent Acyclic Allene (A “Carbodicarbene”): A Strong Donor Ligand

Abstract

Pushed to the limit: Pushing CC π bonds to the breaking point by using a push–push substitution pattern forces allenes to bend (see structure; C light blue, N dark blue). An acyclic allene featuring a CCC bond angle of 134.8° has been isolated in which the typically sp‐hybridized central carbon atom approaches a configuration that has two lone pairs of electrons, and acts as a very strong η1‐donor ligand for transition metals.

Chirality transfer in metal-catalysed intermolecular addition reactions involving allenes

“…This complex could evolve to a bent-allenegold complex transition state TS1, which is proposed to be the rate-determining transition state. 19 After that, two possible pathways are possible: the first one could explain the chirality transfer and would be the direct conversion of TS1 to TS2 without the intervention of a reaction intermediate in a two-step, no intermediate process. This might be the main mechanism at high concentrations of nucleophiles, leading to higher enantiomeric excesses in the final product; the second pathway would account for the racemization of the chiral starting allene, and implies the conversion of TS1 to a planar, cationic gold complex 24 that then suffers the nucleophilic attack, through a traditional two-step outer sphere process.…”

Optical and XPS evidence for the electrochemical generation of an N-heterocyclic carbene and its CS2adduct from the ionic liquid [bmim][PF6]

“…[31][32][33][34] Recently, the coordination chemistry space of NHCs has been further expanded to include non-metals where p-block elements were shown to be stabilized by the coordination of NHCs. [35][36][37][38] Finally, NHCs proved to be highly effective organocatalysts and have been utilized in a wide range of organic reactions. [39][40][41] Traditionally, deprotonation of imidazolium salts using a strong base such as NaH, KOtBu, etc.…”

Mono- and Polynuclear Boron Dications

“…In order to verify the generation of [33] + prior to the formation of [34] 2+ , Himmel's group also carried out a series of quenching studies and isolated several phosphine-coordinated boron cations [HB(hpp) 2 BPR 3 ][HB(C 6 F 5 ) 3 ] ( [35][HB(C 6 F 5 ) 3 ]) from slow addition of B(C 6 F 5 ) 3 to the toluene solution consisting of 32 and phosphine. 67 On the other hand, [35] + cannot be generated from addition of phosphine to [34] 2+ , suggesting the existence of the monomeric intermediate [33] + upon hydride abstraction of 32.…”

“…67 On the other hand, [35] + cannot be generated from addition of phosphine to [34] 2+ , suggesting the existence of the monomeric intermediate [33] + upon hydride abstraction of 32.…”