Heterodimetallic palladium(II) compounds containing terdentate [Csp2(ferrocene),N,N′]− ferrocenyl ligands

The reaction of the novel ferrocenyl Schiff base containing an amino group as pendant arm: [(η5-C5H5)Fe{(η5-C5H4)CHNCH2CH2CH2NMe2}] (1) with palladium(II) salts is reported. Treatment of 1 with the stoichiometric amount of Na2[PdCl4] produced: cis-[Pd{(η5-C5H5)Fe{(η5-C5H4)CHNCH2CH2CH2NMe2}Cl2] (2). However, when the reaction is performed in the presence of sodium acetate it leads to mixtures of 2 and [Pd{[(η5-C5H3)CHNCH2CH2CH2NMe2]Fe(η5-C5H5)}Cl] (3). Compound 3 arises from the activation of the σ[Csp2 (ferrocene)H] bond. Further treatment of 3 with deuteriated pyridine (py-d5) or triphenylphosphine (PPh3) produced the cleavage of the PdN(amine) bond and the formation of the neutral compounds: [Pd{[(η5-C5H3)CHNCH2CH2CH2NMe2]Fe(η5-C5H5)}Cl(L)], with L=py-d5 (4) or PPh3 (5). The reaction of 3 with Tl[BF4] in acetone followed by the addition of PPh3 yielded [Pd{[(η5-C5H3)CHNCH2CH2CH2NMe2]Fe(η5-C5H5)}(PPh3)][BF4] (6). NMR-studies reveal that the ligand acts as a neutral bidentate (N,N′) group, in 2, as a monoanionic bidentate [Csp2 (ferrocene), N]−, in 4 and 5 or terdentate [Csp2 (ferrocene),N,N′]− ligand, in 3 and 6. The X-ray crystal structures of 2 and 3 are also reported and confirm the mode of binding of the ligand to the palladium.