Labelling Studies to Determine Product Formation from Reactions of CO and Hydrogen Catalysed by Ru Clusters and Rh Complexes

Reaction of CO with hydrogen in the presence of [Ru 3 (CO) 12 ], KI and N -methylpyrrolidone produces small amounts of methanol under mild conditions. Using D 2 the methanol is CD 3 OD confirming that it is a product of CO hydrogenation. In the presence of added H 2 O, CH x D 1- y OH/D ( y =0–3) are produced. Carrying out the same reaction in the presence of MeI water and RhCl 3 · x H 2 O ( x =3–4) produces ethanoic acid in a slow reaction which continues for at least 64 h. The effects of different reaction parameters are discussed and labelling using 13 CH 3 I shows that some of the ethanoic acid originates from sources other than MeI whilst labelling with D 2 , CD 3 I, and/or D 2 O suggest that some originates from CO and H 2 . Electrospray mass spectrometry and high pressure infra-red spectroscopic studies show that the main species present in catalytic solutions are [HRu 3 (CO) 11 ] − , [HRu 4 (CO) 13 ] − and [Ru(CO) 3 I 3 ] − for methanol carbonylation, [Ru(CO) 3 I 3 ] − and [RhI 2 (CO) 2 ] − for ethanoic acid production. A reaction carried out in the absence of [Ru 3 (CO) 12 ] gave similar results to a reaction in which it was added, suggesting that the entire process may be catalysed by rhodium complexes alone.