C–H activation of diphenylphosphinoaryl-derivatives with dimethyltetrakis(trimethylphosphine)iron(II)

Fe(CH3)2(PMe3)4 reacts with 1-(diphenylphosphino)naphthalene or benzyldiphenylphosphine within 4 h at 20 °C to give the novel metallated methyl iron complexes Fe(CH3){P(C6H5)2(C10H6)}(PMe3)3 (1) and Fe(CH3){(C6H4)CH2P(C6H5)2}(PMe3)3 (3), respectively, via selective activation of the C–H bond of the pre-chelating ligands. The complexes are thermally unstable releasing metal through a reductive elimination of the aromatic backbone and leading to a C,C-coupling product that is regiospecifically methylated, namely 8-methyl(diphenylphosphino)naphthalene (2). Carbonylation (1 bar, 20 °C, 1 h) of complex 1 effects monosubstitution of a trimethylphosphine ligand trans to the metallated 8-C atom to afford Fe(CH3){P(C6H5)2(C10H6)}(CO)(PMe3)2 (4). The remaining methyl group in the parent complex 1 reacts with trimethylsilylethyne and tert-butylethyne affording the new complexes 5 and 6 bearing an alkynyl substituent trans to the diphenylphosphino anchoring group. The complexes 1 and 3–6 are diamagnetic and possess octahedral coordination geometry. All novel complexes were fully characterized by spectroscopic methods and by X-ray diffraction.