Cross-coupling reactions using Pd-NHC (NHC = N-heterocyclic carbene) catalysts are discussed in this critical review and examined in terms of catalytic activity and how these have permitted advances in the area as they developed (95 references).

The novel 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene (hydroxy) copper ([Cu(IPr)(OH)]) exhibits a versatile capacity to activate numerous X-H bonds including all major hybridizations of C-H (i.e., sp, sp 2 , sp 3 ), N-H, P-H, O-H, S-H, and one example of M-H (M = Mo) bonds. This reactivity also includes the cleavage of the Si-N and Si-C bonds to form unprecedented Cu-centered complexes.

We describe an efficient system for the direct partial oxidation of methane, ethane, and propane using iodate salts with catalytic amounts of chloride in protic solvents. In HTFA (TFA = trifluoroacetate), >20% methane conversion with >85% selectivity for MeTFA have been achieved. The addition of substoichiometric amounts of chloride is essential, and for methane the conversion increases from <1% in the absence of chloride to >20%. The reaction also proceeds in aqueous HTFA as well as acetic acid to afford methyl acetate. (13)C labeling experiments showed that less than 2% of methane is overoxidized to (13)CO2 at 15% conversion of (13)CH4. The system is selective for higher alkanes: 30% ethane conversion with 98% selectivity for EtTFA and 19% propane conversion that is selective for mixtures of the mono- and difunctionalized TFA esters. Studies of methane conversion using a series of iodine-based reagents [I2, ICl, ICl3, I(TFA)3, I2O4, I2O5, (IO2)2S2O7, (IO)2SO4] indicated that the chloride enhancement is not limited to iodate.

Greenhouse gas makes good: A simple copper‐mediated protocol has been developed where NH or CH bonds can be directly functionalized using an easily prepared catalyst. The novel [1,3‐bis(2,6‐diisopropylphenyl)imidazol‐2‐ylidene]copper(I) hydroxide, [Cu(IPr)(OH)], permits the facile activation and carboxylation of NH and CH bonds with pKa values of less than 27.7 (see scheme).

The performance of 16-electron ruthenium complexes with the general formula Cp*Ru(L)X (in which L = phosphine or N-heterocyclic carbene ligand; X = Cl or OCH 2 CF 3 ) was explored in azide−alkyne cycloaddition reactions that afford the 1,2,3-triazole products. The scope of the Cp*Ru(P