Synthesis and characterization of M[Mn(CO) 4DF] and M[Mn(CO) 4DM] (M  Li, Na, (PPh 3) 2N; DF = dimethyl fumarate, DM = dimethyl mal

Abstract

The complexes M[Mn(CO) 4DF] ( 1) and M[Mn(CO) 4DM] ( 2) (M  Li ( a), Na ( b), (PPh 3) 2N (PPN) ( c); DF = dimethyl f DM = dimethyl maleate) were prepared by photochemical reactions of M[Mn(CO) 5] with the appropriate olefin, or by the metathesis reactions of (Li or Na)[Mn(CO) 4DF] and (Li or Na)[Mn(CO) 4DM] with [PPN]Cl. They were characterized by a combination of elemental analysis and IR and 1H and 13C{ 1H} NMR spectroscopy. Complexes 1a, 1b, 2a, and 2b catalyze the isomerization of free DM to DF in THF under reflux for 2–4 days. By contrast, 1c and 2c are catalytically inactive under comparable experimental conditions. Studies on the catalysed isomerization revealed that 1a and 1b exchange ligated DF with free DM in THF at 47–50δC over several days, whereas 1c does not. All three complexes 2a, 2b, and 2c isomerize to 1a, 1b, and 1c, respectively, in THF at 45–55δC o ver se of DM in the coordination sphere of 1, conversion of the resultant 2 back to 1, and replacement of ligated DF by free DM.