6533b872fe1ef96bd12d392f

RESEARCH PRODUCT

INSERTION OF ISOCYANIDES INTO THE PALLADIUM CARBON BOND OF C-2-PALLADATED HETEROCYCLES - SYNTHESIS OF TRANS-[PDCL(C(RN)=NR) (PPH3)2] COMPLEXES (RN = 2-PYRIDYL, 2-PYRAZYL - R = ALKYL OR ARYL GROUP)

subject

description

The titles complexes trans-[PdCl{C(RN)NR}(PPh3)2] (RN = 2-pyridyl (2-py), R = p-C6H4OMe, Me; RN = 2-pyrazyl (2-pyz), R = p-C6H4OMe) can be prepared by reaction of the N-protonated compounds, cis-[PdCl2(RNH)(PPh3] (RNH = 2-pyridylium (2-pyH) or 2-pyrazylium (2-pyzH) group), with PPh3, followed by addition of the isocyanide CNR and deprotonation with triethylamine, in a molar ratio Pd/PPh3/CNR/NEt3 of 1/1/1/1.1. The reaction sequence involves the successive formation of the cationic intermediates trans-[PdCl(RNH)(PPh3)2]+, trans-[Pd(RNH)(CNR)(PPh3)2]2+ and trans-[Pd(RN)(CNR)(PPh3)2]+, which were isolated and characterized as perchlorate salts for RN = 2-pyridyl. In the final step the coordinated isocyanide of trans-[Pd(RN)(CNR)(PPh3)2]+ undergoes migratory insertion into the Pd-RN σ bond, promoted by the chloride ions progressively displaced by the entering neutral ligands from cis-[PdCl2(RNH)(PPh3)]. The resulting products were characterized by conventional spectroscopic techniques and, for RN = 2-pyridyl and R = p-C6H4OMe, also by ligand substitution reaction at the palladium center and by protonation and coordination of the p-methoxyphenylimino(2-pyridyl)methyl group with strong mineral acids (HClO4, HCl) and ZnCl2, respectively.