Understanding Structure Does Not Always Explain Reactivity: A Phosphinoamide Anion Reacts as an Iminophosphide Anion

The aminophosphine C6H4(o-CN)NHPPh2, 1, containing an electron-withdrawing nitrile group, was prepared from the lithiation of 2-aminobenzonitrile followed by addition of Ph2PCI. Lithiation of 1 using (n)BuLi affords the anion [Ph2PN(Li)C6H4(o-CN)(thf)]2, 2. Compound 2 reacts with Ph2PCI or Mel to afford C6H4(o-CN)N=PPh2-PPh2, 3, and [C6H4(o-CN)N=PPh2(CH3)(Lil)(C2H5O)]2, 4, respectively. In these products new P-P and P-C bonds have been formed rather than N-P and N-C bonds. The structures of 1-4 have been determined by single-crystal X-ray diffraction analysis, and the synthetic results are discussed in terms of the structural data and NMR spectroscopic studies.