Group VIII transition metal complexes with the chiral diphosphazane ligand (S)-α-(Ph2P)2N(CHMePh): Synthesis and structural characterization

The chiral ligand S-(Ph2P)2N(CHMePh) reacts with Ni(CO)4 in benzene solution to yield the mononuclear complex [Ni(CO)2{κ2-(PPh2)2N(CHMePh)}] (1). The reactions of the chiral ligand with the solvated complexes [(η5-C5Me5)MCl(solvent)2]BF4 (M = Rh, Ir) or with the binuclear complex [{(η6-C6Me6)RuCl}2(μ-Cl)] in the presence of a chloride scavenger, give cationic complexes of the type [(ηn-ring)MCl{κ2-(PPh2)2N(CHMePh)}]BF4 [ηn-ring = η5-C5Me5; M = Rh (2), Ir (3). η6-C6Me6; M = Ru (4)]. The 31P NMR spectra of compounds 2–4 show two signals corresponding of two phosphorus nuclei with different chemical environments. The related complex [(η5-C5H5)Fe(CO){κ2-(PPh2)2N(CHMePh)}]BF4 (5) was prepared by reaction of the ligand with the complex [(η5-C5H5)Fe(CO)2I] in toluene following by a metathesis with AgBF4. This compound exhibits only one signal in the 31P NMR spectra at room temperature, which splits into two signals at low temperature (213 K). The crystal structures of complexes 2, 3 and 5 have been determined by X-ray diffraction studies. All complexes show the presence of an intramolecular π-stacking interaction. The separation between least-squares planes defined by the two intramolecularly stacked phenyl rings are in the range 3.318–3.649 Å.