This species, + features norbornane ligand bound in a bidentate fashion to a Rh + centre and is formed via the crystal-to-crystal reaction of the diene precursor with hydrogen gas. Andy Weller at the University of YorkĬalculations have provided complementary structural and spectroscopic data ( 13C, IR) to support of the first example of a crystallographically characterized σ-alkane complex. Transition Metal Alkane sigma Complexes and Amineborane Chemistry Current research aims to extend this reactivity to lower fluorinated species and to different nucleophiles other than hydride. The use of N-aryl substituted NHCs is the key to this unusual selectivity as they provide a 'pocket' that can stabilise a highly negatively charged fluoride centre that is formed upon C–F bond cleavage. Calculations show this unusual ortho-selectivity arises from a nucleophilic attack mechanism where the hydride ligand (and not the metal) acts as the reacting species. An example is the hydrodefluorination of C 6F 5H to give 1,2-C 6F 4H 2 catalysed by species. NHC ligands often confer enhanced reactivity on metal complexes. Mike Whittlesey at the University of Bath Ruthenium N-Heterocyclic Carbene (NHC) Complexes as Hydrodefluorination Catalysts However, the cleavage of normally inert bond has its own intrinsic interest and the study of NHC ligands has provided insight into fundamental bond activation processes, including C–H, C–N and even C–C activation.
We are interested in understanding the factors that control these processes, so that improved catalysts can be designed. However, experimental studies by have shown that NHC ligands are often non-innocent and can undergo a variety of intramolecular bond activaton reactions. N-heterocyclic carbenes (NHCs) are popular ligands in organometallic chemistry and homogeneous catalysis, largely due to their strong donor capacity and the idea that NHCs are less prone to ligand degradation processes compared to related phosphine complexes. Transition-Metal-Main Group Heterobimetallic Chemistry Igor Larrosa of the University of Manchester. Current efforts in this area focus on the catalytic functionalisation of C–H bonds in collaboration with Prof. Dai Davies at the University of Leicester We have developed the concept of the ambiphilic metal-ligand activation (AMLA) mechanism, whereby an agostic interaction renders the C–H bond susceptible to an intramolecular deprotonation. However, facile C–H activation can occur at electron deficient metal centres in the presence of a chelating base, such as acetate. Hydrocarbons are very abundant and extremely cheap and so would make ideal chemical feedstocks – were it not for their notoriously low chemical reactivity.