6533b7d8fe1ef96bd126b6cb

RESEARCH PRODUCT

The oligomerisation of phenylacetylenes with rhodium(I) and P ligands as the catalytic system

subject

description

Abstract The dependence of the oligomerisation of phenylacetylene to cyclotrimers and dimers upon a Rh(I) complex with different P ligands as the catalytic system has been studied. The influence of substituents in the phenyl ring of the substrate has been examined as well. A selective cyclotrimerisation of phenylacetylenes is achieved with [1,5-C6H10RhCl]2 as the catalyst. A decrease of the selectivity appears with very bulky o-substituents or a substitution in the 2,6-position of phenylacetylene. [P]-control maps indicate a mono-association of the ligand accompanied by a reduced activity of the system. The second association of a P ligand results in an inhibition of the cyclotrimerisation in favour of a very effective dimerisation of the phenylacetylenes. The ratio of the two dimers varies with electronic and steric changes of the substrate and with the cone angle of the P ligand. Different experimental data indicate that the oxidative addition of a terminal alkyne and a Rh hydride addition to a π-bonded phenylacetylene are rate determining steps.