With tridentate phosphite ligands applied as cocatalysts, the kinetically controlled rhodium-catalyzed isomerizing hydroformylation reaction of internal olefins yields the linear aldehyde with a selectivity> 90% which is combined with surprisingly high reaction rates. Information on the kinetics of the individual reaction steps involving 2-pentene and a mixture of internal octenes, respectively, as substrates has been acquired by in situ high pressure IR spectroscopy and GC. From the IR and also HPNMR spectroscopic data, an equilibrium occurring during catalysis at 20 bar CO/H2(1:1) and 120�C, between mono- and dicarbonyl hydrido complexes is reasoned, pointing to a hemilabile ligand character. Synthesis and characterization of further rhodium complexes revealed the capability of the ligands to exert a variety of coordination modes. The structure of a sterically strained tridendate phosphite chelate rhodium hydrido complex diastereoisomer has been resolved by X-ray analysis. The facile synthesis of the new ligand family takes benefit from a spontaneously occuring selective phosphite transesterification step. A given seven-membered phosphacycle is opened and the essential 1,3,2-dioxaphosphinine ligand substructure, which is based on 1,8,9-trihydroxyanthracene is formed.A short comparison with respect to the performance and available structural data between the catalyst type described here and results from literature which are related to the hydroformylation of internal olefins will be given. The easy access to the new ligands, together with their highly desired influence on the rhodium metal center qualifies them as candidates for an industrial application.

Olefin isomerization hydroformylation reaction with hemilabile tridentate phosphite modified rhodium catalysts

248th National Meeting (2014)

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