Cu effect on Fe catalyst

The use of Fe based catalyst in reactions that tipically are in the field of Pd chemisty has been logically subject of a great interest in recent years. Potencial toxicity and higher costs are obvious drawbacks for the use of Pd instead of Fe, so the idea is very interesting. I first conscienciously heard of this in last june in ChemSpecEurope Barcelona, in a lecture by Bedford, at Bristol, and had it in mind to check it next time I’ll face a catalytic coupling or a Heck reaction.

A few days ago, however, a very interesting comment appeared in OPRD quoting a paper from Buchwald and Bolm (Angew.Chem.Internat.Ed.,2009,48,5586) where Fe was used as catalyst in a coupling reaction. Interestingly, the reaction performance negatively correlated with the purity of iron (the impurities are meant to be other metals, such as Cu). In the same Angewandte number (Angew.Chem.Internat.Ed.,2009,48,5691) Bolm showed that coupling reactions can behave quite well in the presence of Cu, even at ppm levels, indicating that the actual active species could very well be Cu-based instead of Fe-based.