PHOSPHORAMIDITES - NOVEL MODIFYING LIGANDS IN RHODIUM-CATALYZED HYDROFORMYLATION

The phosphoramidites 2-9 have been applied as modifying ligands in rho dium-catalysed hydroformylation of oct-1-ene and styrene. Monodentate phosphoramidites 2-5 gave rise to catalysts with average rates of 1000 mol [mol Rh](-1) h(-1) and maximum selectivities of 65% to the linear product nonanal for the hydroformylation of oct-1-ene (P 20 bar CO/H- 2, T 80 degrees C, [oct-1-ene] approximate to 1 M). Styrene was hydrof ormylated (T 40 degrees C, P 20 bar CO/H-2) at rates up to 150 mol [mo l Rh](-1) h(-1) and a selectivity for the branched 2-phenylpropanal of 93%. Using diphosphoramidite modified catalysts a maximum rate of 120 0 mol.[mol Rh](-1).h(-1) for oct-1-ene was observed for 9, with 91% re gioselectivity for the linear product. At 40 degrees C styrene was hyd roformylated at rates up to 25 mol [mol Rh](-1) h(-1) and with selecti vities for the branched aldehyde of 89%. Characterization of the rhodi um complexes showed that formation of rhodium hydride complexes is slo w and incomplete under the conditions applied for the monosphoshoramid ites. The diphosphoramidite ligands all form bidentate hydrido-rhodium complexes. The diphosphoramidite ligands 6-9 coordinate bis-equatoria lly in the trigonal bipyramidal rhodium complexes, which accounts for the high regioselectivities.