Reactions involving Two-coordinate Phosphorus

The first l,3i2-diazaphosphinines 65 have been prepared as shown.These very reactive molecules are versatile precursors to 1,2-azaphosphinines 66 and phosphinines 67, which are formed by highly regioselective [4 + 2] cycloadditions between 65 and alkynes. The 2-halo-1,3,2-diazaphospholenes 68, when heated above 250 C, eliminated butyl halide to form 1,3,2-diazaphospholes 69. A 1,2,4-thiadiphosphole (70) and the 1,2,4-selenadiphospholes have been prepared and characterised by X-ray crystal structure determinations. 

An ionic 2-chloro-l,3,2-diazaphospholene (72) was prepared from a silicon precursor (73). Since the saturated analogue 74 was covalent, the phosphenium ion 72 is probably stabilised by having an aromatic 6n electron structure. The phosphadiazonium compound 75 with a sterically hindered phenol or aniline gave the phosphenium ions 76 this constitutes a new preparative route to phosphenium ions. A series of phosphenium ions (77), stabilised by two intramolecular dative P-N bonds, has been prepared, and the X-ray crystal structure of one (77, X = H, Y = PFg) determined.  

The new P-alkoxyiminophosphine 78 was prepared from the P-chloro analogue and shown to exist in a trans configuration, contrary to other known P-alkoxyiminophosphines. Some very hindered diphosphenes (79) have been prepared and their behaviour upon reduction with alkali metals or at an electrode studied.  

Kimura, T. Nakano, S. Matsunaga, G. Iwasaki, A. Ogawa, and K. Hayakawa, Tetrahedron Lett., 1997,38, 3543. 

Hoffmann, O. Wagner, A. Goller, T. dark, and M. Regitz, Chem. Ber.lRecueil, 1997, 130, 711. 

---