Synthesis and Ligand Properties of 1-Phosphaethenyl-2-phosphanylferrocenes

( S )-1-Phosphaethenyl-2-diarylphosphanylferrocenes with planar chirality (Fc(CH═PMes*)PAr 2: PAr 2 = PPh 2 ( 3a ), P(1-naphthyl)Ph ( 3b )) are prepared in high yields from optically active 2-phosphanylferrocenecarboxaldehydes by the phospha-Peterson reactions with Mes*P(Li)SiMe 3 in THF. The stereochemistry of 3b is determined by X-ray diffraction analysis. Compounds 3a and 3b readily react with [PtMe 2 (μ-SMe 2 )] 2 in Et 2 O to afford dimethyl complexes with bidentate coordination of these ligands (PtMe 2 (L): L = 3a ( 4a ), 3b ( 4b )). The X-ray structure of 4b reveals almost identical trans-influence of the phosphaethenyl and phosphanyl groups, showing comparable σ-donating abilities of those components. Treatment of 3a and 3b with [Pd(η 3 -allyl)(μ-Cl)] 2 in CH 2 Cl 2 in the presence of AgOTf forms the corresponding π-allyl complexes [Pd(η 3 -allyl)(L)]OTf (L = 3a ( 5a ), 3b ( 5b )), respectively, which are mixtures of diastereomers with endo- and exo-oriented π-allyl ligands. Complex 5a catalyzes hydroamination of 1,3-cyclohexadiene with aniline in toluene in the presence of 5 Å molecular sieves at room temperature, giving N -cyclohexen-3-ylaniline in 84% yield.