Phenoxide-assisted P–C bond cleavage in PdCl2(PPh3)2 under very mild conditions

PdCl2(PPh3)2 reacted with NaOAr (Ar = Ph, p-tolyl) at 0 °C to afford PdCl(Ph)(PPh3)2, instead of PdCl(OAr)(PPh3)2, in 12–16% isolated yields based on Pd. The structure was confirmed by NMR and X-ray crystallography. GC–MS analysis of the reaction solution revealed that OPPh2(OAr), OPPh(OAr)2, and OP(OAr)3 are formed, while NMR studies indicated that PdCl(Ph)(PPh3)2 is produced when PdCl(OAr)(PPh3)2 decomposes. The reaction of PdCl2(PPh3)2 with Bu3Sn(OC6H4-p-OMe) also gave PdCl(Ph)(PPh3)2 in 8% isolated yield. These results suggest that PdCl(OAr)(PPh3)2 is highly labile and the aryloxy ligand exchanges with the phenyl groups in triphenylphosphine even under very mild conditions.

Graphical abstractPdCl2(PPh3)2 reacted with NaOAr (Ar = Ph, p-tolyl) at 0 °C to afford PdCl(Ph)(PPh3)2, instead of PdCl(OAr)(PPh3)2, in 12–16% isolated yields based on Pd. It is likely that the reaction proceeds via an intermediate, PdCl(OAr)(PPh3)2, and subsequent aryloxy–phenyl exchange that involves P–C bond cleavage.Figure optionsDownload full-size imageDownload as PowerPoint slide