In situ high-pressure P-31{H-1} NMR studies of the hydroformylation of 1-hexene by RhH (CO)(PPh3)(3)

The hydroformylation of 1-hexene with syngas (40 bar of 1:1 CO/H-2) in the presence of the catalyst precursor RhH(CO)(PPh3)(3) has been studied by hig h-pressure NMR spectroscopy in a 10 mm sapphire tube equipped with a Ti-all oy valve. Except for RhH(CO)(2)(PPh3)(2), no direct observation of labile i ntermediates involved in the catalytic cycle has been detected; however as many as four rhodium resting states have been seen, and some factors contro lling their formation/interconversion/inhibition have been identified. The information gathered from this in situ investigation is particularly releva nt to a better understanding of the inhibiting action of the CO pressure as well as the positive action of PPh3 addition.