Check out p 8 of:
https://www.thevespiary.org/rhodium/Rhodium/pdf/nickel-on-charcoal.pdf
There you can see the use of a compound called 1,1'-bis(diphenylphosphanyl)-ferrocene (DPPF) as a ligand in organometallic reactions. I was intrigued by this, so I fetched the article about the aromatic amination by heterogeneous Ni°/C catalysis.
The authors states the following: "Given the importance of aryl amines in a variety of contexts (e.g. pharmaceuticals), a potentially scaleable heterogenous process which utilizes inexpensive chloride precursors and nickel rather than palladium may provide a welcomed complement to existing protocols."
Yeah right, I guess nickel is a pretty damned sure cheaper than palladium. But what about the 1,1'-bis(diphenylphosphanyl)-ferrocene?
Looking at the molecular structure, I don't think this can be a cheap compound.
Can someone please look up how much this DPPF costs (say 5 grams)? The reaction requires this specific ligand, they tried it with others - but it didn't work ...