Unprecedented rhodium-catalyzed stereoselective polymerization of "carbenes" from ethyl diazoacetate (EDA) to give high molecular mass poly(ethyl 2-ylidene-acetate) is described. The mononuclear, neutral [(N,O-ligand)M(I)(cod)] (M = Rh, Ir) catalytic precursors for this reaction are characterized by (among others) single-crystal X-ray diffraction. These species mediate formation of a new type o...

Metal carbene complexes have been at the forefront of organic and organometallic synthesis and are instrumental in guiding future sustainable chemistry efforts. While classical Fischer and Schrock type carbenes have been intensely studied, compounds that do not fall within one of these categories have attracted attention only recently. In addition, applications of carbene complexes rarely take ...

Reactivity umpolung allows us to consider nontraditional bond disconnections. We report herein that treatment of an alpha-haloaldehyde with a nucleophile in the presence of catalytic amounts of nucleophilic carbenes results in an internal redox reaction giving rise to a dehalogenated acylating agent as an intermediate by a new reaction manifold. A brief illustration of the scope of this reactio...

In the presence of stoichiometric or catalytic amounts of [M{N(SiMe3 )2 }2 ] (M=Fe, Co), N-heterocyclic carbenes (NHCs) react with primary phosphines to give a series of carbene phosphinidenes of the type (NHC)⋅PAr. The formation of (IMe4 )⋅PMes (Mes=mesityl) is also catalyzed by the phosphinidene-bridged complex [(IMe4 )2 Fe(μ-PMes)]2 , which provides evidence for metal-catalyzed phosphinidene...

N-Heterocyclic carbenes, prepared in situ from diarylimidazolium salts, serve as highly effective catalysts for the generation of reactive homoenolates from alpha,beta-unsaturated aldehydes. The catalyst-bound homoenolate reacts with electrophilic aldehydes leading, via the key intermediacy of an activated carboxylate, to gamma-butyrolactones in good yields and stereoselectivities. Importantly,...

The steric and electronic influence of backbone substitution in IMes-based (IMes = 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene) N-heterocyclic carbenes (NHC) was probed by synthesizing the [RhCl(CO)₂(NHC)] series of complexes to quantify experimentally the Tolman electronic parameter (electronic) and the percent buried volume (%V(bur), steric) parameters. The corresponding ruthenium-indeny...

Eight new N-heterocyclic carbenes (NHCs) featuring substituted naphthyl side chains were synthesized. These molecules are present in solution as a stable mixture of anti and syn conformers. Through careful tuning of the substituents on position 2 and 2,7 of the naphthyl moieties, it was possible to synthesize molecules that display a strong preference for the anti conformation (up to 95:5). Thi...

The use of two metal systems cis-Pt(NHC)(2)Me(2) and cis-Ir(NHC)(CO)(2)Cl help to highlight the flexibility of a series of cycloalkyl-substituted N-heterocyclic carbene ligands (ICy, ICy(7), ICy(8), ICy(12)). Bond dissociation enthalpies of several N-heterocyclic carbenes (NHCs) in cis-Pt(NHC)(2)Me(2) are estimated. Electronic and steric parameters of the ICy(n) ligands are quantified and discu...

N-Heterocyclic carbenes (NHCs) have emerged as a powerful class of organocatalysts that mediate a variety of organic transformations. The Benzoin reaction constitutes one of the earliest known carbon-carbon bond-forming reactions catalysed by NHCs. The rapid growth of NHC catalysis in general has resulted in the development of a variety of benzoin and benzoin-type reactions. An overview of such...

The preparation of a 1,3-bis(2,6-terphenyl)imidazol-2-ylidene, IDitop (Ditop=2,6-bis(4-tolyl)phenyl-) is reported. Several late transition metal complexes as well the selenium adduct were prepared to study and compare stereoelectronic properties other well-known N-heterocyclic carbenes (NHCs). A steric character taken from crystal structure data adducts reveals high degree flexibility. Prelimin...