D. Barney Walker

Alkyne Activation Using Bimetallic Catalysts

Bimetallic catalysts are capable of activating alkynes to undergo a diverse array of reactions. The unique electronic structure of alkynes enables them to coordinate to two metals in a variety of different arrangements. A number of well-characterised bimetallic complexes have been discovered that utilise the versatile coordination modes of alkynes to enhance the rate of a bimetallic catalysed process. Yet, for many other bimetallic catalyst systems, which have achieved incredible improvements to a reactions rate and selectivity, the mechanism of alkyne activation remains unknown. This chapter summarises the many different approaches that bimetallic catalysts may be utilised to achieve cooperative activation of the alkyne triple bond.

The advantages of covalently attaching organometallic catalysts to a carbon black support: recyclable Rh(i) complexes that deliver enhanced conversion and product selectivity.

Pure carbon black (CB) was covalently attached to a bidentate nitrogen coordination motif with a carbon-carbon bond by spontaneous reaction with an in situ generated ligand precursor. The functionalized support was treated with [Rh(CO)2(μ-Cl)]2 to form a heterogeneous carbon-based support covalently linked to a well defined Rh(i) coordination complex. The hybrid material was characterized using X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), Infrared (IR) spectroscopy and inductively coupled plasma mass spectrometry (ICP-MS). The CB-supported Rh(i) catalyst was active in both hydroamination and dihydroalkoxylation reactions achieving turnover numbers approaching 1000 and was readily recycled. The selectivity of an intramolecular dihydroalkoxylation reaction was significantly improved by covalently anchoring the catalyst to the CB surface.