Synthesis and characterization of some rhenium complexes with the new mixed phosphorus–nitrogen donor ligand NPh(CH2CH2PPh2)2

Abstract

Reaction of NPh(CH₂CH₂Cl)₂ with LiPPh₂ at 0 °C yields the new mixed nitrogen–phosphorus donor ligand NPh(CH₂CH₂PPh₂)₂(L). Reaction of [ReOCl₃(AsPh₃)₂] with L in CH₂Cl₂ at room temperature gives [ReOCl₃L]3. Reaction of [ReCl₃(MeCN)(PPh₃)₂] with L in refluxing benzene gives [ReCl₃L]4. Treatment of 3 or 4 with LiAlH₄ at 0 °C in Et₂O affords [ReH₅L]5. Protonation of 5 with HBF₄·OEt₂ in CD₂Cl₂ at 193 K gives [ReH₆L]⁺6. Deprotonation of 6 with NEt₃ regenerates 5 quantitatively. Compound 5 shows a ¹H NMR T₁(minimum) value of 78 ms at 250 MHz, consistent with a classical structure having only terminal hydride ligands, while 6 shows a T₁(minimum) value of 10 ms, suggesting a non-classical structure containing one or more η²-H₂ ligands.