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

## TL;DR

This paper shows how hydrocarbyl groups can migrate from palladium to phosphorus ligands, forming new phosphorane complexes with unique bonding.

## Contribution

The study reveals a new nonspectator ligand reactivity pathway in palladium chemistry involving phosphorus ligands.

## Key findings

- Hydrocarbyl groups from Pd(II) migrate to tricoordinate phosphorus ligands, forming isolable palladaphosphoranes.
- 31P NMR shifts correlate with hydrocarbyl hybridization, explained by variations in P─C bond orbitals.
- Halide exchange preserves palladaphosphorane connectivity, suggesting stability and synthetic utility.

## Abstract

Migration of palladium‐bound hydrocarbyl ligands to tricoordinate phosphorus ligand P(N(o‐N(2‐pyridyl)C6H4)2) (L) is demonstrated across a series of Pd(II) organometallic complexes bearing Csp, Csp
2, and Csp
3 groups. Treatment of ligand L with cis‐[(TMEDA)PdI(C6H5)], cis‐[(TMEDA)PdBr(CH2C6H5)], [(η3‐C3H5)PdCl]2, and trans‐[PdBr(C≡C─C6H5)(PPh3)2], respectively, results in migration of the hydrocarbyl group from Pd to P, yielding isolable (σ4‐P)─Pd palladaphosphoranes: LAllyl•PdCl
, LBn•PdBr
, LPh•PdI
, and LCCPh•PdBr
. 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. 31P 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 (σ3─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.

Well‐defined migration of Csp, Csp
2, and Csp
3 hydrocarbyls from Pd(II) compounds to a nontrigonal P(III) ligand scaffold is reported. The structural and spectroscopic features of the resulting complexes reveal a conserved Pd─P interaction. The results demonstrate the nonspectator role of structurally constrained tricoodinate P(III) ligands in palladium chemistry.