Influences of the substituents at the iminic carbon atoms (hydrogen versus methyl) upon the properties of ferrocenylimines and their cyclopalladated derivatives
Abstract
Ferrocenylimines of general formula [Fe(η5-C5H5)(η5-C5H4CRNR′)](R = Me, R′= Ph 1a, C6H4Me-2 1b, C6H4Me-4 1c, CH2Ph 1d, CH2C6H4Me-2 1e, CH2C6H4Cl-2 1f, CH2CH2Ph 1g or 1-C10H71h; R = H, R′= Ph 1i, C6H4Me-2 1j, C6H4Me-4 1k, CH2C6H4Me-2 1l, CH2C6H4Cl-2 1m or 1-C10H71n) have been prepared and characterized. Addition of these ligands to methanolic solutions of Na2[PdCl4], and sodium acetate trihydrate in a 1 : 1 molar ratio, results in the formation of the di-µ-chloro bridged cyclopalladated complex [{[graphic omitted]R′)](µ-Cl)}2]2a–2n. Reaction of compounds 2a–2n with triphenylphosphine in benzene yields more soluble monocyclopalladated derivatives [[graphic omitted]R′)}Cl(PPh3)]3a–3n. Proton, 13C and 31P NMR spectroscopic studies on these complexes reveal that cyclopalladation occurs on the ferrocenyl moiety, thus producing five-membered metallacycles containing the CN bond (endo-type structures). The crystal structures of compounds 1a, 1i and 3g have been determined. Complex 1a is triclinic, space group P with a= 10.152(3), b= 12.169(3), c= 12.239(3)Å, α= 90.45(2), β= 100.56(2) and γ= 102.72(2)°. Compound 1i is monoclinic, space group Cc, with a= 5.876(3), b= 37.298(9), c= 12.640(4)Å and β= 103.26(4)°. The complex [[graphic omitted]CH2CH2Ph)}Cl(PPh3)]·CH2Cl23g is monoclinic, space group P21/n with a= 20.343(2), b= 9.133(1), c= 19.714(2)Å and β= 97.17(1)°, and its crystal structure confirms the formation of a five-membered palladocycle fused with the ferrocenyl moiety. The influence of the substituents R (H or Me) and R′ upon the spectroscopic and structural properties of the free ligands and the cyclopalladated complexes is also discussed.