Synthesis, Structural Characterization of Ferrocenyl Iminophosphines and Amidophosphines as Well as Their Application in the Suzuki Reaction

Ferrocenyliminophosphine 1 and 1,1′-bisferrocenyliminophosphine 2 were easily prepared from the condensation of formylferrocene or 1,1′-diformylferrocene with 2-(diphenylphosphino) aniline. The following reduction of imine group by LiAlH4 led to the formation of the corresponding ferrocenyl amidophosphines 3 and 4. The new ligands 2-4 were well characterized by IR, 1H NMR, 31P NMR spectra, elemental analysis, and ESI-MS. The catalytic activity of all the ligands with palladium compounds in the Suzuki reaction was evaluated. Ligand 1, in combination with Pd(OAc)2, was found to be the most effective for the Suzuki reaction of aryl bromides with phenylboronic acid. Typically, the use of 0.1% (molar fraction) of Pd(OAc)2/ligand 1 in the presence of two equivalents of K2CO3 as base in toluene at 110°C provided good to excellent yields of the coupled products.