Comparative reactivity of palladium(0) complexes generated in situ in mixtures of triphenylphosphine or tri-2-furylphosphine and Pd(dba)2

For PPh3, mixtures of Pd(dba)(2) and nTFP (TFP = tri-2-furylphosphine, n greater than or equal to 2) in DMF and THF (S) lead to the formation of Pd(dba)(TFP)(2), SPd(TFP)(3) in equilibrium with SPd(TFP)(2). The substitution of dba by the phosphine in Pd(dba)L-2 to form SPdL3 is easier for L = TPF than for L = PPh3, The less ligated complex SPd(TFP)(2) is the reactive species in the oxidative addition with phenyl iodide. In THF, (Pd(dba)(2) + nTFP), a mixture often used as a catalyst promoter in several synthetic organic reactions, is found to be less reactive than {Pd(dba)(2) + nPPh(3)} for small values of n (n. = 2 or 4) whereas it is more reactive for higher values of n (n > 6). Conversely, in DMF, {Pd(dba)(2) + nTFP} is always found to be more reactive than {Pd(dba)(2) + nPPh(3)} whatever n (n greater than or equal to 2).