ACTIVATION OF SIGMA(C-H) BONDS IN FERROCENYL-IMINES AND BIS(FERROCENYL)-IMINES PROMOTED BY PALLADIUM

Ferrocenylimines of general formula [Fe(eta(5)-C5H5){eta(5)-C5H4CH2CH2N=CR(R')}] [R = H, R' = Ph 1a, C6H4Cl-2 1b, C6H3Cl2-2,6 1c, C(6)H(2)Me(3)-2,4,6 1d or (eta(5)-C5H4)Fe(eta(5)-C5H5) 1e, R = Me, R' = (eta(5)-C5H4) Fe(eta(5)-C5H5) 1f] were prepared by condensation of 2-ferrocenylethylamine and the corresponding aldehyde (1a-1e) or acetylferrocene (1f). Cyclopalladation reactions of these substrates gave different kinds of metallacycle depending on the nature of the ligand. In particular, endocyclic five-membered palladacycles containing a sigma(Pd-C-sp2,C-phenyl) or a of sigma(Pd-C-sp2,C-ferrocene) were obtained from 1a, 1b and 1e, 1f respectively. However, for the ferrocenylimines in which the ortho positions of the aryl ring are blocked by either chlorine (1c) or methyl (1d) groups, mixtures of palladated compounds containing a sigma(Pd-C-sp1,C-ferrocene) and a sigma(Pd-(csp2,phenyl)) (for 1c) or a sigma(Pd-C-sp3,C-aliphatic) bond (for 1d) were obtained. The molecular structure of [Pd{C6H4CH=NCH2CH2(eta(5)-C5H4)Fe(eta(5)-C5H5)}Cl(PPh(3))]. CH2Cl2 was determined by X-ray crystallography: triclinic, space group <P(1)over bar>, with a = 9.995(1),b = 11.308(2), c=15.747(2) Angstrom, alpha=96.85(1), beta=99.05(1) and gamma=95.99(1)degrees. This confirms the formation of a five-membered palladacycle fused with the phenyl ring.