Strong π-acceptor ligands in rhodium-catalyzed hydroformylation of ethene and 1-octene: Operando catalysis

Strong π-acceptor N-pyrrolylphosphoramidite and pyrrolylphosphine mono- and bidentante ligands were applied in ethene hydroformylation using a stoichiometric gas mixture CO/H₂/ethene 1:1:1. Very fast reactions (TOF up to 29.5 × 103 mol mol^-1 h^-1, 13-fold faster than triphenylphosphine) and excellent selectivities were obtained. The pyrrolylphosphine derivatives of SPANphos and Xantphos, pySPAN and pyXANT, were used in 1-octene hydroformylation. The electronic character of these ligands improved both activities and regioselectivities compared with the phenyl-substituted ligands. HPNMR and HPIR showed that both pySPAN and pyXANT favor the formation of bisequatorial [RhH(CO)₂(ligand)] complexes under catalytic conditions.