ACTIVATION OF SIGMA(C-H) BONDS IN FERROCENYLHYDRAZONES DERIVED FROM ACETYLFERROCENE

The synthesis and characterization of the novel ferrocenylhydrazones: [(eta(5)-C5H5)Fe{(eta(5)-C5H4)-C(CH3)=N-NHR}] (R = C6H4-4-NO2 (1a), C6 H4-4-Cl (1b), C6H4-2-CH3 (Ic), C6H3-2,4-(NO2)(2) (Id) or C6H3-2,5-Cl-2 (1e)) is described. These compounds react in methanol with Na-2(PdCl4 ) and sodium acetate trihydrate in a 1:1:1 molar ratio at room tempera ture, giving the di-mu-chlorobridged cyclopalladated complexes: 5)-C5H 3)-C(CH3)=N-NHR]Fe(eta(5)-C5H5)}(mu-Cl)}](2) (2). Addition of tripheny lphosphine (PPh3) to benzene suspensions of compounds 2, produced the cleavage of the di-mu-chlorobridges and the formation of a(5)-C5H3)-C( CH3)=N-NHR]Fe(eta(5)-C5H5)}Cl(PPh3)}] (3). NMR studies (H-1 and P-31) on compound 3 revealed the formation of a (5,5) bicyclic system derive d from the fusion of a five-membered palladacycle and the ferrocenyl m oiety. The X-ray crystal structure of H3)=N-NH(C6H3-2,5-Cl-2)]Fe(eta(5 )-C5H5)}Cl(PPh3)}] (3e) is also reported and confirms the formation of a five-membered palladacycle with a sigma(Pd-C-sp2,C-ferrocene) bond. (C) 1997 Elsevier Science S.A.