Reactivity of a Dinuclear Pd^I Complex [Pd₂(μ-PPh₂)(μ₂-OAc)(PPh₃)₂] with PPh₃: Implications for Cross-Coupling Catalysis Using the Ubiquitous Pd(OAc)₂/nPPh₃ Catalyst System

[PdI2(μ-PPh2)(μ2-OAc)(PPh3)2] is the reduction product of PdII(OAc)2(PPh3)2, generated by reaction ‘Pd(OAc)2’ with two equivalents PPh3. Here, we report that PPh3 results in a nuanced disproportionation reaction, forming [Pd0(PPh3)3] and phosphinito-bridged PdI-dinuclear complex, namely [PdI2(μ-PPh2){κ2-P,O-μ-P(O)Ph2}(κ-PPh3)2]. The latter complex proposed to form abstraction an oxygen atom from acetate ligand at Pd. A mechanism for formal putative PdII species observed PdI postulated. Upon mixture [Pd0(PPh)3] [PdI2(μ-PPh2){κ2-P,O-μ-P(O)Ph2}(κ-PPh3)2] 2-bromopyridine, former Pd0 undergoes fast oxidative addition while dinuclear converts slowly tripalladium cluster, type [Pd3(μ-X)(μ-PPh2)2(PPh3)3]X, overall 4/3 oxidation state per Our findings reveal complexity associated precatalyst activation step ubiquitous ‘Pd(OAc)2’/nPPh3 catalyst system, implications cross-coupling catalysis.