Versatility in the mode of coordination {(N), (N,O)−, (C,N)− or (C,N,O)2−} of [(η5-C5H5)Fe{(η5-C5H4)–CHN–(C6H4-2OH)}] to palladium(II)

The study of the reactivity of the ferrocenyliminoalcohol [(η5-C5H5)Fe{(η5-C5H4)–CHN–(C6H4-2OH)}] (1b) with Na2[PdCl4] or Pd(OAc)2 has allowed the isolation and characterization of the heterotrimetallic complexes: trans-[Pd{(η5-C5H5)Fe[(η5-C5H4)–CHN–(C6H4-2OH)]}2Cl2] (2b), [Pd{[(η5-C5H3)–CHN–(C6H4-2O)]Fe(η5-C5H5)}{(η5-C5H5)Fe[(η5-C5H4)–CHN–(C6H4-2OH)]}] (3b) and trans-[Pd{(η5-C5H5)Fe[(η5-C5H4)–CHN–(C6H4-2O)]}2] (4b). Ligand 1b acts as a (N) (in 2b) or a (N,O)− (in 4b) ligand; while in 3b the two units of the iminoalcohol exhibit simultaneously different modes of binding {(N) and [C(sp2, ferrocene),N,O]2−}. The crystal structures of 2b · 3H2O and 3b · 1/2CHCl3 are also reported and confirm the mode of binding of the ligand in these compounds. The relative importance of the factors affecting the preferential formation of products (2b–4b) is also discussed. The study of the reactivity of 3b with PPh3 has enabled the obtention of the cyclopalladated complexes [Pd{[(η5-C5H3)–CHN–(C6H4-2O)]Fe(η5- C5H5)}(PPh3)] (6b) and [Pd{[(η5-C5H3)–CHN–(C6H4-2OH)]Fe(η5-C5H5)}Cl(PPh3)] (7b), in which 1b behaves as a [C(sp2, ferrocene),N,O]2− (in 6b) or [C(sp2, ferrocene),N]− (in 7b) ligand. Treatment of 3b with MeO2C–CC–CO2Me produces [Pd{[(MeO2C–CC–CO2Me)2(η5-C5H3)–CHN–(C6H4-2O)]Fe(η5-C5H5)}] (8b), that arises from the bis(insertion) of the alkyne into the σ[Pd–C(sp2, ferrocene)] bond. The comparison of the results obtained for 1b and [C6H5–CHN–(C6H4-2OH)] (1a) has allowed to establish the influence of the substituents on the imine carbon on their reactivity in front of palladium(II) as well as on the lability of the Pd-ligands bond. 57Fe Mössbauer studies of 2b–4b and 6b provide conclusive evidence of the effect induced by the mode of binding of 1b on the environment of the iron(II).

The experimental strategies to control selectively the formation of a wide variety of novel palladium(II) complexes containing the ferrocenyliminoalcohol [(η5-C5H5)Fe{(η5-C5H4)–CHN–(C6H4-2OH)}] (1b) acting as a (N)−, (N,O)−, [C(sp2, ferrocene),N]− or [C(sp2, ferrocene),N,O]2− ligand are described.Figure optionsDownload as PowerPoint slide