Masked iminophosphide anion: Synthesis and versatile reactivity

Article abstract of DOI:10.1021/om00002a047

The unprecedented iminozirconiophosphorane 3, Me₂P(ZrCp₂Cl)=N-Ar (Ar = 2,4,6-t-Bu₃C₆H₂), a masked iminophosphide, has been prepared by reacting chloroiminophosphane 2, Cl-P=N-Ar, with Cp₂ZrMe₂. Insertion reactions into the zirconium-phosphorus bond take place when 3 is reacted with nitriles, paraformaldehyde, or carbon disulfide, giving rise to iminophosphoranes. Formal insertion into the nitrogen-zirconium bond occurs when 3 is treated with isocyanides RNC (R = Me₃SiCH₂, cyclohexyl), affording phosphanes. A single-crystal X-ray structure of one of them has been determined. Addition of pyridine-HCl, methyl iodide, N-bromosuccinimide, or various chlorophosphanes to 3 leads to iminophosphoranes via exchange reactions taking place directly on the phosphorus center of 3. Addition of the Eschenmoser salt [H₂C=NMe₂]Cl to 3 affords a mixture of iminophosphorane and phosphonium salt. 3 reacts with triflic acid or methyl trifluoromethane-sulfonate, giving exclusively phosphonium salts. Reactions involving the thermodynamically stable form of 3, i.e. the phosphane 5, Me₂P-N(ZrCp₂Cl)(2,4,6-t-Bu₃C₆H ₂), occur when 3 is treated with the chloroiminophosphane 2 with formation of a phosphanyliminophosphane. Treatment of 3 with NiCl₂ or PdCl₂ gives rise to the complexes 28a (M = Ni) and 28b (M = Pd), [Me₂P-N(H)-2,4,6-t-Bu₃C₆H₂] ₂MCl₂.