COVALENT ALTERNATIVES FOR THE ELUSIVE IMINOPHOSPHONIUM CATION - CRYSTAL-STRUCTURES OF PCL(NPRI2)2NPH.ALCL3 AND P(NPRI2)2[NPH(SO2CF3)]O

Reactions between diaminoiminophosphinic chlorides and the chloride-abstracting agents AlCl3 and Ag(SO3CF3) have been comprehensively examined as potential routes to the three-co-ordinate iminophosphonium cation. However, bis(dialkylamino)(phenylimino)phosphinic chlorides react to give the covalent phosphoryl systems PCl(NR2)2NPh.AlCl3 and P(NR2)2[NPh(SO2CF3)]O respectively, in quantitative yield. The AlCl3 complexes are also prepared quantitatively from the reaction of P(NPr(i)2)2+AlCl4- with PhN3 (Staudinger reaction). All compounds have been comprehensively characterised and the structures of the isopropyl derivatives confirmed by X-ray crystallography. Crystal data: PCl(NPr(i)2)2NPh.AlCl3, space group P2(1), a = 8.719(2), b = 15.553(2), c = 9.509(2) angstrom, beta = 102.73(2)-degrees, Z = 2, R = 0.029; P(NPr(i)2)2[NPh(SO2CF3)]O, space group P2(1)/n, a = 10.594(3), b = 13.222(2), c = 17.084(3) angstrom, beta = 97.71(2)-degrees, Z = 4, R = 0.048. The results indicate that the three-co-ordinate diaminoiminophosphonium cation is thermodynamically unstable with respect to the observed alternative covalent structures, and that steric shielding is responsible for the stability of the analogous diaminomethylenephosphonium cation.