Photoinduced oxidation of coordinated ligands in trans-carbonylchlorobis(triphenylphosphine)rhodium. Generation of a decarbonylation agent

Five-coordinate dicarbonyl complexes of rhodium(I): [RhX(CO)2(PPh3)2] (X = Cl, Br, I)

“…For personal use only. presence of excess PPh, (22), and loss of CO from l a is far from facile (23). Consequently it is proposed that catalytic decarbonylation occurs by initial loss of a PPh, ligand from l a .…”

Catalytic decarbonylation of aldehydes using iron(II) porphyrin complexes, and the crystal structure of (5,10,15,20-tetraphenylporphinato)bis(tri-n-butylphosphine)iron(II)

“…Stoichiometric decarbonylation of aldehydes (and acid chlorides) by platinum metal complexes is well documented (5), but it is generally difficult to remove the coordinated carbonyl from the resulting complex either thermally (5) or photolytically (6). However, effective thermal catalysts (in refluxing toluene) for such decarbonylation were first provided by Rh(P-P): complexes, because the R~(CO)(P-P) : species generated 'ABBREVIATIONS.…”

Catalytic decarbonylation of aldehydes

“…Small amounts of alkenes and H2 are also formed from higher saturated aldehydes; for example, 14% 1-hexene is produced from heptanal.2 The mechanism for the stoichiometric decarbonylation is presumably similar to that proposed for acyl halides.7•8 The reaction cannot be made sufficiently catalytic at useful temperatures because 7-RhCl(CO)(PPh3)2 does not lose carbon monoxide and the active species [RhCl(PPh3)2] cannot be regenerated thermally9 or photochemically. 10 The decarbonylation reaction can be made catalytic for high boiling aldehydes with 1 or z-RhCl(CO)(PPh3)2 (vide infra) at temperatures >200 °C,6 but CO loss is proposed2 to occur from the acyl intermediate, which results from oxidative addition of aldehyde to i-RhCl(CO)(PPh3)2. Results reported in this communication will show that clean homogeneous catalytic decarbonylation of aldehydes using cationic rhodium(I) complexes of chelating diphosphine ligands occurs at temperatures considerably lower than with 1 and with long-term catalyst stability.…”