C _sp , C _sp ² , and C _sp ³ Hydrocarbyl Group Migration from Pd(II) to P(III): Accessing Metallophosphoranes via Nonspectator Ligand Reactivity

Abstract

Abstract Migration of palladium‐bound hydrocarbyl ligands to tricoordinate phosphorus ligand P(N(o‐N(2‐pyridyl)C 6 H 4 ) 2 ) ( L ) is demonstrated across a series of Pd(II) organometallic complexes bearing C sp , C sp 2 , and C sp 3 groups. Treatment of ligand L with cis ‐[(TMEDA)PdI(C 6 H 5 )], cis ‐[(TMEDA)PdBr(CH 2 C 6 H 5 )], [(η 3 ‐C 3 H 5 )PdCl] 2 , and trans ‐[PdBr(C≡C─C 6 H 5 )(PPh 3 ) 2 ], respectively, results in migration of the hydrocarbyl group from Pd to P, yielding isolable (σ 4 ‐P)─Pd palladaphosphoranes: L Allyl •Pd Cl , L Bn •Pd Br , L Ph •Pd I , and L CCPh •Pd Br . The mechanistic pathway of the palladaphosphorane formation was investigated by in situ NMR experiments and DFT calculations, suggesting an α‐migration mechanism. Halide exchange with NaBr or NaI affords the corresponding bromide and iodide congeners without disrupting the palladaphosphorane connectivity. 31 P NMR chemical shifts correlate systematically with the identity and hybridization of the hydrocarbyl group, and electronic structure analyses attribute observed trends to variations in the s/p hybrid compositions of the local P─C bond orbitals. This work establishes an underappreciated facet in the reactivity landscape of Pd complexes bearing tricoordinate phosphorus (σ 3 ─P) ligands by demonstrating their ability to undergo nonspectator metal‐to‐ligand group transfer, with implications for designing bifunctional ligand architectures capable of cooperative catalysis.