Manganese catalysts Stille coupling

The catalyst used is often palladium (0) (like Pd(PPh3)4, Pd2(dba)3), or a source of palladium (II) (like Pd(OAc)2, BnPdCl(PPh3)2 to name a few that gets reduced to the active species palladium(O) in situ. Methods using other metals like manganese, copper, and nickel have been reported the latter has been applied for instance in the successful Stille coupling of unreactive aryl chlorides as well as in the coupling of unactivated primary and secondary alkyl halides. ... 

Other transition metals, like manganese and nickel, have been used in the Stille coupling (as additive or as replacement of palladium). As we will see later, nickel proved to be very powerful in replacing palladium as catalyst and is very promising in terms of expanding the scope of the reaction. 

Moreover, copper(l) halides or manganese(ll) bromide efficiently catalysed the Stille reaction of arylstannanes with aryl halides without any palladium catalyst added [87,88]. In contrast to MnBr2, manganese(II) chloride was proved as a less effective catalyst, whereas manganese(II) iodide-mediated reactions failed to give any cross-coupled products [88]. The latter achievements dramatically extend the economy of the Stille reaction since the use of, generally very expensive, palladium chemicals is completely avoided. 

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