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

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Fe(CH 3) 2(PMe 3) 4 reacts with 1-(diphenylphosphino)naphthalene or benzyldiphenylphosphine within 4 h at 20 °C to give the novel metallated methyl iron complexes Fe(CH 3){P(C 6H 5) 2(C 10H 6)}(PMe 3) 3 ( 1) and Fe(CH 3){(C 6H 4)CH 2P(C 6H 5) 2}(PMe 3) 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(CH 3){P(C 6H 5) 2(C 10H 6)}(CO)(PMe 3) 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.