Rhodium phosphino-enolate complexes as chemo- and regioselective catalysts for the hydroformylation of styrenes

Abstract The catalytic utility of [κ 2 -{3- i Pr 2 P -2- O -indene}Rh(COD)] (COD = η 4 −1,5-cyclooctadiene) 1a in the hydroformylation of styrenes was examined. Complex 1a was shown to be an effective pre-catalyst in benzene and tetrahydrofuran, exhibiting good conversions to aldehyde and high branched-to-linear selectivity for styrene, 4-chlorostyrene, and 4-methylstyrene under reasonably mild conditions (1000 psi syngas; 1.8 mol% Rh, 45 °C, 2–5 h). Under analogous conditions, the iridium congener of 1a proved inactive for hydroformylation. The synthesis and crystallographic characterization of the new complex [κ 2 -{2- i Pr 2 P C 6 H 4 O }Rh(COD)] 2 is also reported; the catalytic performance of 2 in the hydroformylation of styrene was found to be comparable to that of 1a under similar catalytic conditions.