A novel and convenient strategy to separate, recover and reuse N-heterocyclic carbene catalysts in transesterification reactions has been developed.

The mesomeric betaine imidazolium-1-ylphenolate forms a borane adduct with tris(pentafluorophenyl)borane by coordination with the phenolate oxygen, whereas its NHC tautomer 1-(2-phenol)imidazol-2-ylidene reacts with (triphenylphosphine)gold(I) chloride to give the cationic NHC complex [Au(NHC)2][Cl] by coordination with the carbene carbon atom. The anionic N-heterocyclic carbene 1-(2-phenolate)...

Compared to earlier single site catalysts, greatly enhanced rates of electrocatalytic water oxidation by the Ru carbene catalyst [Ru(tpy)(Mebim-py)(OH(2))](2+) (tpy = 2,2':6',2''-terpyridine; Mebim-py = 3-methyl-1-pyridylbenzimidazol-2-ylidene) have been observed. The mechanism appears to be the same with proton coupled electron transfer (PCET) activation to Ru(V)=O(3+) followed by O-O coupling...

The asymmetric unit of the title N-heterocyclic carbene compound, C(22)H(32)N(4) (2+)·2PF(6) (-), consists of one half of the N-heterocyclic carbene dication and one hexa-fluoro-phosphate anion. The dication lies across a crystallographic inversion center. The imidazole ring is twisted away from the central benzene ring, making a dihedral angle of 76.23 (6)°. The hexa-fluoro-phosphate anions li...

The title compound, [CrZr(C(5)H(5))(2)(C(2)H(3)O)Cl(CO)(5)], consists of two metal centres, with a (penta-carbonyl-chromium)oxymethyl-carbene group coordinating as a monodentate ligand to the zirconocene chloride. π-Delocalization through the Zr-O-C=Cr unit is indicated by a short Zr-O distance [2.041 (3) Å] and a nearly linear Zr-O-C angle [170.5 (3)°]. Mol-ecules are aligned with their mol-ec...

Gold(I) N-heterocyclic carbene (NHC) complexes were obtained in good yields from the corresponding silver complexes by treatment with [AuCl(PPh3)] following the commonly used silver carbene transfer route. The silver complexes were synthesized from the benzimidazolium halide salts by the in situ reactions with Ag2O in dichloromethane as a solvent at room temperature. All gold complexes have bee...

In the title complex, [PdI(2)(C(24)H(31)N(3))(2)]·2C(6)H(6), the Pd(2+) ion is located on an inversion centre in a slightly distorted square-planar geometry. The angle between the I(2)C(2) square plane and the mean plane of the N-heterocyclic carbene ring is 79.8 (2)°, with I-Pd-C-N torsion angles of -81.1 (6) and -78.2 (5)°. The Pd-carbene and Pd-I distances are 2.016 (6) and 2.5971 (10) Å, re...

Sulfur-containing nitriles have important research value in the life sciences due to their diverse biological activities resulting from the sulfur and cyano functional groups. Herein, a copper-catalyzed cyanothiolation of N-tosylhydrazones with thiocyanates to generate a-arylthioalkanenitriles bearing sulfur-substituted quaternary carbon center atoms has been described. This novel protocol invo...

[reaction: see text]. A novel convergent approach to fully functionalized ring C allocolchicinoids is developed which is based on the benzannulation reaction of Fischer carbene complexes with alkynes. The efficacy of this strategy was established with the conversion of bromide 1a (R1 = Me, R2 = H) to the biaryl phenol 3a (R = Me, R(L) = Pr, R(S) = H) via the carbene complex 2a. Bromide 1b (R1 =...

For the past dozen years, homogeneous gold catalysis has evolved from a little known topic in organic synthesis to a fully blown research field of significant importance to synthetic practitioners, due to its novel reactivities and reaction modes. Cationic gold(I) complexes are powerful soft Lewis acids that can activate alkynes and allenes toward efficient attack by nucleophiles, leading to th...