A large solvent polarity effect on the rate of singlet to triplet intersystem crossing (ksT) has been observed in the carbenes, diphenylcarbene (DPC) and dicycloheptadienylidene (DCHD)it is found that both ksT and the energy splitting (A&T) separtaing the singlet and triplet states decrease as the solvent polarity increases for the aromatic carbenes. This “inverse” gap effect, i.e. the time for...

Transition metal and organic catalysts have established their own domains of excellence. It has been expected that merging the two unique domains should provide complimentary or unprecedented opportunities in converting simple raw materials to functional products. N-heterocyclic carbenes alone are excellent organocatalysts. When used with transition metals such as copper, N-heterocyclic carbene...

Lewis acidic yttrium(III) and titanium(IV) derivatives of anionic, metal-tethered carbenes apparently act as bifunctional catalysts for the polymerisation of D,L-lactide, using a combination of Lewis acid and base functionalities to initiate ring opening of the cyclic monomer; the alcohol- and amino-functionalised carbenes from which they derive provide models for the first insertion step, and ...

Cyanogen halides are known substances for the cyanating reaction. There are a few evidences for bromination reaction too. On the other hand carbenes are known as very important substances due to their remarkable reactions. Unfortunately carbenes at room temperature are very unstable and there is not a simple method for preparation of them. In most cases the isolation is not possible. We have re...

Carbenes. First examples of anionic cyclic (alkyl)(amino)carbenes bearing B(CN)3 or C2F5BF2 as N-substituents are reported by Udo Radius, Maik Finze et al. in their Research Article (e202300056). Their stereo-electronic parameters were also evaluated.

N atom, thus providing carbenes derived from pyrazolium, isothiazolium, and even quinolinium salts that contain a stabilizing heteroatom in a remote position (G-J in Figure 1). Recently, carbenes such as K, which are comprised of only one heteroatom and lack delocalization through the heterocycle, have been discovered as versatile ligands, thus constituting another important class of carbenes w...

We prepared a series of imidazolium-substituted uracil-anions which are members of the class of cross-conjugated heterocyclic mesomeric betaines. They are in tautomeric equilibrium with their N-heterocyclic carbenes, uracil-6-yl-imidazol-2-ylidenes. These carbenes can be trapped by reaction with sulfur, selenium, as well as by triethylborane and triphenylborane, respectively. The latter trappin...

The N-heterocyclic carbenes (NHC) now hold a preferredligand status in organic and organometallic chemistry. Their role in catalysis continues to grow. When the editorial staff at the Beilstein Journal of Organic Chemistry contacted me to act as a guest editor for the thematic series “N-Heterocyclic carbenes”, I was more than happy to accept what appeared to me to be a simple and exciting endea...

For the title complexes we discuss the results of DFT calculations for (i) the molecular and electronic structures, (ii) the rotational barriers of the carbenes around the Fe=Ccarb bond (Erot), and (iii) the binding energies of the carbenes (De). Where available, the calculated properties of the Fe=Ccarb bonds are compared with previous theoretical and experimental data of some prototypical ca...